Those not-ATP sanctioned invitationals in the 70s and early 80s are one of the biggest problems for evaluation in Tennis history. We had some threads about it. Several were really important tournaments, which were simply not sanctioned by the ATP for rivaling reasons, like the Frankfurt Event in 1979 or later the Antwerp Golden Racket (or even much later the Grand Slam Cup).
I was live at one 4 men event in Essen in late 1978, where Borg, Laver, Panatta and Gerulaitis played. This was imo an exhibition, Laver had lost his equipment on the flight and borrowed rackets and Fila shirts from Borg. The younger players went to the disco after days play. A week later however, i saw a 8 men event in Germany on TV, where Borg beat i think Fibak in the final. Looked very much like a real tournament. I agree with Kiki: We should include them, if they were not one night stands, and examine them further.
Very clarifying - thanks. Here's a list of invitationals I included in Borg's titles from '76-'80 (pretty much pulled from wikipedia). I'm definitely curious to get folks' takes on which side of the real tournament v. exo they fall under:
8+ player draws
October 19-21, 1978: Hamburg - Rothenbaum Tennis Club (Carpet)
Borg d. Wojtek Fibak 6–1, 6–1 in the final.
September 28-30, 1979: Marbella - European Championships of Tennis (Clay)
Borg d. Adriano Panatta 6–2, 6–2, 7–5 in the final.
November 26-29, 1979: Milan – Masters Brooklyn Chewing Gum (Carpet)
Borg d. John McEnroe, 1–6, 6–1, 6–4 in the final.
November 29 - December 2, 1979: Frankfurt - Cup Invitational Tennis Round Robin (Carpet)
Borg d. Jimmy Connors 6–3, 4–6, 6–3, 6–4 in the final.
Less than 8 player draws
September 14-16, 1976: Guadalajara, Jalisco Tennis Invitational Round Robin (Clay)
Borg d. Ilie Năstase 6–3, 6–3 in the final.
September 17-19, 1976: Mexico Marlboro Tennis Round Robin (Clay)
Borg d. Ilie Năstase 7–6, 0–6, 6–1 in the final.
October 11-15, 1976: Hilton Head World Invitational Tennis Classic (Clay)
Borg d. Arthur Ashe 6–1, 6–2 in the final.
November 3-5, 1976: Chicago Olsonite Tennis Classic (Carpet)
Borg d. John Newcombe by unknown score in the final.
November 6-7, 1976: Detroit Michigan Pro Tennis 4-men invitational (Carpet)
Borg d. Rod Laver 6–3, 6–1 in the final.
November 24-28, 1976: Copenhagen Pondus Cup Invitational Round Robin (Carpet)
Borg d. Wojtek Fibak 7–5, 3–6, 7–6, 7–5 in the final.
February 12-13, 1977: Cincinnati Riverfront Coliseum Invitational Round Robin - 3-men (Carpet)
Borg d. Rod Laver 6–7, 6–3, 6–2 in the final.
September 27-30, 1977: Hilton Head World Invitational Tennis Classic (Clay)
Borg d. Roscoe Tanner 6–4, 7–5 in the final.
March 7-9, 1978: Gothenburg Scandinavian Cup (Carpet)
Borg d. Vitas Gerulaitis 6–4, 1–6, 6–3 in the final.
April 18-20, 1978: Copenhagen Pondus Cup Invitational (Carpet)
Borg d. Vitas Gerulaitis 2–6, 6–4, 6–4 in the final.
April 21-23, 1978: Tokyo Suntory Cup (Carpet)
Borg d. Jimmy Connors 6–1, 6–2 in the final.
August 14-15, 1978: Menton French Riviera Invitational (Clay)
Borg d. Guillermo Vilas 6–4, 6–3 in the final.
August 16-17, 1978: Fréjus Arena Trophy (Clay)
Borg d. Guillermo Vilas 7–6, 7–5 in the final.
October 16-18, 1978: Essen Gruga Hall International (Carpet)
Borg d. Vitas Gerulaitis 6–3, 7–6 in the final.
October 28-29, 1978: Manila Smash-78 Tennis (Clay)
Borg d. Vitas Gerulaitis 6–2, 7–6 in the final.
November 23-24, 1978: Antwerp European Tennis Championships (Carpet)
Borg d. Tom Okker 6–4, 6–3 in the final.
March 6-7, 1979: Vienna Velo Cup Tennis – 4-men invitational (Carpet)
Borg d. John McEnroe 3–6, 6–1, 6–4 in the final.
September 26-27, 1979: Essen Gruga Hall International – 4-men invitational (Carpet)
Borg d. Ilie Năstase 6–1, 6–4 in the final.
October 2-7, 1979: Netherlands - 5 city (Final at Rotterdam) Roxy Tennis Round Robin – 5-men (Carpet)
Borg d. Eddie Dibbs 6–3, 6–0 in the final.
November 24-25, 1979: Brussels Belgian Cup – 4-men invitational (Carpet)
Borg d. Adriano Panatta 6–1, 7–6 in the final.
December 14-16, 1979: Cairo Egypt's First International Round Robin (Clay)
Borg d. Ismail El Shafei 6–2, 6–3 in the final.
March 8-9, 1980: Stuttgart Cup-80 – 4-men invitational (Carpet)
Borg d. Adriano Panatta 6–2, 5–7, 6–1 in the final.
October 25-26, 1980: Berlin West Berlin Cup – 4-men invitational (Carpet)
Borg d. Vitas Gerulaitis 7–6, 6–3 in the final.