8‑Oct‑1979 | Tel Aviv | Hard | F | 46 | | (2)Okker d. Per Hjertquist [SWE] | 6-4 6-3 | | | | | | | | | |
15‑Oct‑1978 | Tel Aviv CH | Hard | F | 47 | 78 | (1)Okker d. (2)Peter Feigl [AUT] | 6-7 6-4 6-2 | | | | | | | | | |
24‑Jul‑1978 | Hilversum | Clay | F | | | (3)Balazs Taroczy [HUN] d. (5)Okker | 2-6 6-1 6-2 6-4 | | | | | | | | | |
31‑Jan‑1977 | Richmond WCT | Carpet | F | 27 | 20 | Okker d. Vitas Gerulaitis [USA] | 3-6 6-3 6-4 | | | | | | | | | |
27‑Oct‑1975 | Paris Indoor | Hard | F | 6 | 7 | Okker d. (2)Arthur Ashe [USA] | 6-3 2-6 6-3 3-6 6-4 | | | | | | | | | |
16‑Jun‑1975 | Nottingham | Grass | F | 10 | 21 | Okker d. Tony Roche [AUS] | 6-1 3-6 6-3 | | | | | | | | | |
21‑Apr‑1975 | Stockholm - WCT | Carpet | F | 9 | 8 | (1)Arthur Ashe [USA] d. (3)Okker | 6-4 6-2 | | | | | | | | | |
11‑Apr‑1975 | Johannesburg - WCT | Hard | F | 9 | 61 | (7)Buster C Mottram [GBR] d. (4)Okker | 6-4 6-2 | | | | | | | | | |
24‑Feb‑1975 | Rotterdam WCT | Carpet | F | 6 | 7 | (1)Arthur Ashe [USA] d. (3)Okker | 3-6 6-2 6-4 | | | | | | | | | |
4‑Nov‑1974 | Stockholm | Hard | F | 5 | 8 | Arthur Ashe [USA] d. Okker | 6-2 6-2 | | | | | | | | | |
26‑Aug‑1974 | Boston | Clay | F | 5 | 8 | Bjorn Borg [SWE] d. Okker | 7-6 6-1 6-1 | | | | | | | | | |
1‑May‑1974 | Acapulco | Carpet | F | 3 | 9 | Okker d. Jan Kodes [CZE] | 6-2 7-6 | | | | | | | | | |
25‑Mar‑1974 | Rotterdam | Carpet | F | 3 | 11 | (2)Okker d. (3)Tom Gorman [USA] | 4-6 7-6(2) 6-1 | | | | | | | | | |
11‑Mar‑1974 | Washington WCT | Carpet | F | 3 | 1 | (1)Ilie Nastase [ROU] d. (2)Okker | 6-3 6-3 | | | | | | | | | |
11‑Feb‑1974 | Toronto WCT | Carpet | F | 4 | 1 | Okker d. (1)Ilie Nastase [ROU] | 6-3 6-4 | | | | | | | | | |
4‑Dec‑1973 | Masters | Carpet | F | 4 | 1 | Ilie Nastase [ROU] d. Okker | 6-3 7-5 4-6 6-3 | | | | | | | | | |
17‑Nov‑1973 | London | Carpet | F | 5 | 1 | Okker d. Ilie Nastase [ROU] | 6-3 6-4 | | | | | | | | | |
21‑Oct‑1973 | Madrid | Clay | F | 6 | 23 | Okker d. Jaime Fillol [CHI] | 4-6 6-3 6-3 7-5 | | | | | | | | | |
30‑Sep‑1973 | Chicago | Carpet | F | 6 | 2 | Okker d. John Newcombe [AUS] | 3-6 7-6 6-3 | | | | | | | | | |
17‑Sep‑1973 | Los Angeles | Hard | F | 8 | 10 | Jimmy Connors [USA] d. Okker | 7-5 7-6 | | | | | | | | | |
16‑Sep‑1973 | Seattle | | F | 8 | 28 | (2)Okker d. (8)John Alexander [AUS] | 7-5 6-4 | | | | | | | | | |
20‑Aug‑1973 | Toronto | Clay | F | | | (3)Okker d. (4)Manuel Orantes [ESP] | 6-3 6-2 6-1 | | | | | | | | | |
23‑Jul‑1973 | Washington | Clay | F | | | (3)Arthur Ashe [USA] d. (1)Okker | 6-4 6-2 | | | | | | | | | |
16‑Jul‑1973 | Hilversum | Clay | F | | | Okker d. Andres Gimeno [ESP] | 2-6 6-4 6-4 6-7 6-3 | | | | | | | | | |
19‑Mar‑1973 | Washington WCT | Carpet | F | | | Okker d. Arthur Ashe [USA] | 6-3 6-7(4) 7-6(3) | | | | | | | | | |
13‑Nov‑1972 | Rotterdam WCT | Carpet | F | | | (2)Arthur Ashe [USA] d. (3)Okker | 3-6 6-2 6-1 | | | | | | | | | |
4‑Nov‑1972 | Stockholm | Hard | F | | | (1)Stan Smith [USA] d. (3)Okker | 6-4 6-3 | | | | | | | | | |
6‑Jul‑1972 | Boston WCT | Hard | F | | | Bob Lutz [USA] d. Okker | 6-4 2-6 6-4 6-4 | | | | | | | | | |
16‑Mar‑1972 | Chicago WCT | Carpet | F | | | (3)Okker d. Arthur Ashe [USA] | 4-6 6-2 6-3 | | | | | | | | | |
10‑Oct‑1971 | Vancouver WCT | | F | | | Ken Rosewall [AUS] d. Okker | 6-2 6-2 6-4 | | | | | | | | | |
10‑Aug‑1971 | Montreal / Toronto | Clay | F | | | (1)John Newcombe [AUS] d. (2)Okker | 7-6 3-6 6-2 7-6 | | | | | | | | | |
1‑Aug‑1971 | Quebec WCT | | F | | | Okker d. Rod Laver [AUS] | 6-3 7-6 6-7 6-4 | | | | | | | | | |
24‑Jul‑1971 | Louisville WCT | Clay | F | | | Okker d. Cliff Drysdale [RSA] | 3-6 6-4 6-1 | | | | | | | | | |
10‑Jul‑1971 | Gstaad | Clay | F | | | John Newcombe [AUS] d. Okker | 6-2 5-7 1-6 7-5 6-3 | | | | | | | | | |
5‑Apr‑1971 | Monte Carlo | Clay | F | | | (3)Ilie Nastase [ROU] d. (1)Okker | 3-6 8-6 6-1 6-1 | | | | | | | | | |
19‑Mar‑1971 | Champions Classic | Carpet | F | | | Rod Laver [AUS] d. Okker | 6-5 6-2 6-1 | | | | | | | | | |
15‑Oct‑1970 | Bonn | | F | | | Rod Laver [AUS] d. Okker | 6-2 6-7 6-2 | | | | | | | | | |
17‑Aug‑1970 | Hamburg | Clay | F | | | (1)Okker d. (3)Ilie Nastase [ROU] | 4-6 6-3 6-3 6-4 | | | | | | | | | |
2‑Aug‑1970 | Hilversum | Hard | F | | | Okker d. Roger Taylor [GBR] | 4-6 6-0 6-1 6-3 | | | | | | | | | |
19‑Jul‑1970 | Leicester | Grass | F | | | Okker d. Roger Taylor [GBR] | 6-1 10-8 | | | | | | | | | |
18‑Jul‑1970 | Gstaad | Clay | F | | | Tony Roche [AUS] d. Okker | 6-3 7-5 6-3 | | | | | | | | | |
12‑May‑1970 | Brussels | Clay | F | | | Okker d. Ilie Nastase [ROU] | 6-3 6-4 0-6 4-6 6-4 | | | | | | | | | |
6‑May‑1970 | Atlanta | Hard | F | | | Okker d. Dennis Ralston [USA] | 6-4 10-8 6-2 | | | | | | | | | |
26‑Jan‑1970 | Auckland | Grass | F | | | Roger Taylor [GBR] d. Okker | 6-4 6-4 6-1 | | | | | | | | | |
13‑Nov‑1969 | Vienna | Hard | F | | | Tony Roche [AUS] d. Okker | W/O | | | | | | | | | |
7‑Nov‑1969 | Paris | Carpet | F | | | (3)Okker d. (4)Earl Butch Buchholz [USA] | 8-6 6-2 6-1 | | | | | | | | | |
2‑Nov‑1969 | Casablanca | | F | | | Tony Roche [AUS] d. Okker | 9-7 6-3 | | | | | | | | | |
3‑Oct‑1969 | Tucson | Hard | F | | | Tony Roche [AUS] d. Okker | 9-7 6-1 | | | | | | | | | |
20‑Aug‑1969 | Newport | Grass | F | | | Okker d. Dennis Ralston [USA] | 4-6 6-5 1-0(1) | | | | | | | | | |
4‑Aug‑1969 | Hamburg | Clay | F | | | Tony Roche [AUS] d. Okker | 6-1 5-7 7-5 8-6 | | | | | | | | | |
3‑Aug‑1969 | Hilversum | Hard | F | | | Okker d. Roger Taylor [GBR] | 10-8 7-9 6-4 6-4 | | | | | | | | | |
27‑Jul‑1969 | Gstaad | Clay | F | | | Roy Emerson [AUS] d. Okker | 6-1 12-14 6-4 6-4 | | | | | | | | | |
18‑Jul‑1969 | Milwaukee | Clay | F | | | Okker d. Marty Riessen [USA] | 6-3 6-4 | | | | | | | | | |
22‑May‑1969 | Amsterdam | Clay | F | | | Okker d. Andres Gimeno [ESP] | 6-4 6-3 | | | | | | | | | |
12‑May‑1969 | Brussels | Clay | F | | | Okker d. Zeljko Franulovic [CRO] | 6-4 1-6 6-2 6-2 | | | | | | | | | |
1‑May‑1969 | Japanese Championships | Carpet | F | | | Okker d. Roy Emerson [AUS] | 6-3 6-5 | | | | | | | | | |
15‑Apr‑1969 | Monte Carlo | Clay | F | | | (2)Okker d. (5)John Newcombe [AUS] | 8-10 6-1 7-5 6-3 | | | | | | | | | |
4‑Apr‑1969 | Johannesburg | Hard | F | | | Rod Laver [AUS] d. Okker | 6-3 10-8 6-3 | | | | | | | | | |
29‑Aug‑1968 | US Open | Grass | F | | | (5)Arthur Ashe [USA] d. (8)Okker | 14-12 5-7 6-3 3-6 6-3 | | | | | | | | | |
18‑Aug‑1968 | Scheveningen | Clay | F | | | Okker d. Jan Hajer [NED] | 6-2 6-3 10-8 | | | | | | | | | |
21‑Jul‑1968 | Gstaad | Clay | F | | | Cliff Drysdale [RSA] d. Okker | 6-3 6-3 6-0 | | | | | | | | | |
8‑Jul‑1968 | Dublin | Grass | F | | | Okker d. Lew Hoad [AUS] | 6-1 6-2 | | | | | | | | | |
10‑Jun‑1968 | Lugano | Clay | F | | | Ion Tiriac [ROU] d. Okker | 6-8 7-5 6-0 | | | | | | | | | |
10‑Jun‑1968 | Saltsjoebaden | | F | | | Okker d. Jan Erik Lundquist [SWE] | 3-6 6-3 7-5 | | | | | | | | | |
29‑May‑1968 | Berlin | Clay | F | | | Manuel Santana [ESP] d. Okker | 6-8 6-4 6-1 6-2 | | | | | | | | | |
6‑May‑1968 | Rome | Clay | F | | | (4)Okker d. (3)Bob Hewitt [RSA] | 10-8 6-8 6-1 1-6 6-0 | | | | | | | | | |
1‑Apr‑1968 | Johannesburg 1 | Hard | F | | | Okker d. Marty Riessen [USA] | 12-10 6-1 6-4 | | | | | | | | | |
18‑Mar‑1968 | Curacao | Hard | F | | | Marty Riessen [USA] d. Okker | 7-5 3-6 9-11 6-2 6-2 | | | | | | | | | |
4‑Mar‑1968 | Barranquilla | Clay | F | | | Okker d. Marty Riessen [USA] | 8-6 6-3 6-3 | | | | | | | | | |
26‑Feb‑1968 | Kingston | Hard | F | | | Okker d. Manuel Orantes [ESP] | 6-2 6-4 | | | | | | | | | |
8‑Jan‑1968 | Bloemfontein | Hard | F | | | Marty Riessen [USA] d. Okker | 7-5 6-3 | | | | | | | | | |
18‑Dec‑1967 | East London | Clay | F | | | Okker d. Mark Cox [GBR] | 9-7 7-5 | | | | | | | | | |
1‑Dec‑1967 | Rio De Janeiro | | F | | | Thomaz Koch [BRA] d. Okker | 6-4 11-9 3-6 6-3 | | | | | | | | | |
12‑Nov‑1967 | Porto Alegre | | F | | | Cliff Richey [USA] d. Okker | 6-4 3-6 6-3 8-6 | | | | | | | | | |
4‑Sep‑1967 | Mamaia | | F | | | Ion Tiriac [ROU] d. Okker | 6-2 7-5 3-6 4-6 6-3 | | | | | | | | | |
19‑Aug‑1967 | Poertschach | Clay | F | | | Okker d. Ingo Buding [GER] | 6-1 6-1 6-2 | | | | | | | | | |
10‑Aug‑1967 | Scheveningen | Clay | F | | | Okker d. Jan Hajer [NED] | 4-6 6-1 6-3 8-6 | | | | | | | | | |
18‑Jul‑1967 | Le Touquet | Clay | F | | | Okker d. Francois Jauffret [FRA] | 6-1 6-0 6-4 | | | | | | | | | |
11‑Jun‑1967 | Bristol | Grass | F | | | Okker d. Cliff Drysdale [RSA] | 6-2 5-7 8-6 | | | | | | | | | |
15‑May‑1967 | Brussels La Rasante | | F | | | Roy Emerson [AUS] d. Okker | 6-3 3-6 7-5 6-4 | | | | | | | | | |
7‑Mar‑1967 | Brussels | | F | | | Okker d. Jimmy Moore [AUS] | 6-2 6-2 6-0 | | | | | | | | | |
20‑Feb‑1967 | Paris Indoors | Carpet | F | | | Okker d. Jan Kodes [CZE] | 6-2 3-6 6-3 6-4 | | | | | | | | | |
14‑Aug‑1966 | Scheveningen | Clay | F | | | Okker d. Jan Hajer [NED] | 11-9 5-7 6-3 | | | | | | | | | |
18‑Jul‑1966 | Hilversum | Clay | F | | | Okker d. Bob Hewitt [RSA] | 6-3 6-3 2-6 6-3 | | | | | | | | | |
14‑Jul‑1966 | Velp | Clay | F | | | Okker d. Ernst Blanke [AUT] | 1-6 6-3 6-2 | | | | | | | | | |
18‑May‑1966 | Brussels | Clay | F | | | Okker d. Bob Carmichael [AUS] | 8-10 6-3 6-3 | | | | | | | | | |
23‑Apr‑1966 | Bournemouth | Clay | F | | | Ken Fletcher [AUS] d. Okker | 7-5 6-4 | | | | | | | | | |
1‑Mar‑1966 | Zuidlaren | Carpet | F | | | Okker d. Robert Wilson [GBR] | 6-1 1-6 6-2 | | | | | | | | | |
27‑Dec‑1965 | Melbourne South Yarra | Grass | F | | | Okker d. Ken Fletcher [AUS] | 6-2 3-6 6-3 | | | | | | | | | |
29‑Aug‑1965 | Tel Aviv Maccabiah Games | Clay | F | | | Okker d. Mike Franks [USA] | 6-4 6-1 6-4 | | | | | | | | | |
9‑Aug‑1965 | Scheveningen | Clay | F | | | Okker d. Evert Schneider [NED] | 6-4 7-5 6-4 | | | | | | | | | |
19‑Jul‑1965 | Hilversum | Clay | F | | | John Newcombe [AUS] d. Okker | 6-2 3-6 6-1 6-4 | | | | | | | | | |
28‑Jun‑1965 | Wimbledon Plate | Grass | F | | | Owen Davidson [AUS] d. Okker | 6-3 8-6 | | | | | | | | | |
7‑Jun‑1965 | Belfast | Grass | F | | | Okker d. Bill Hoogs Iv [USA] | 6-2 12-10 | | | | | | | | | |
31‑May‑1965 | Manchester | Grass | F | | | Okker d. Roger Taylor [GBR] | 7-5 6-3 | | | | | | | | | |
10‑Aug‑1964 | Scheveningen | Clay | F | | | Okker d. Jan Hajer [NED] | 6-2 2-6 7-5 6-3 | | | | | | | | | |
16‑Jul‑1964 | Pescara | Clay | F | | | Okker d. Giordano Majoli [ITA] | 6-3 6-3 | | | | | | | | | |
18‑May‑1964 | Glamorgan | Grass | F | | | Okker d. Gerald Battrick [GBR] | 6-3 6-4 | | | | | | | | | |
13‑Aug‑1962 | Scheveningen | Clay | F | | | Willem Maris [NED] d. Okker | 6-4 6-8 1-6 6-1 7-5 | | | | | | | | | |