Yes, Björn Borg is a definite GOAT-contender on grass, his records are so eye-popping.
Borg wins junior Wimbledon 1972, loses at tight four setter as a 16-year-old (!) to double-Wimbledon-champ Emerson in a qualifying round on USO old, slow grass.
1973 is Borg's first real year on the pro-tour as a 16-17 year old. First real grass court tourney he enters asa full pro is Beckenham and reaches the final losing to the finalist at Wimbledon that year Metreveli, reaches the QF at Wimby being up 2 sets to 1 against Taylor. Thereafter he does this at the USO to 1972-finalist Ashe:
Quite a bit of successful and constant 2nd serve volleying from Borg there and ultimate proof of his capability with this tactic on these different grass-surfaces against contemporary champion-level opposition.
In December 1973 he travels to Australia for AO 1974, without any prep and loses in R3 to eventual finalist to Phil Dent. Practicing on Aussie grass his skills improve and he enters Auckland Open 1974, best of five in all rounds tourney and there wins his 1st pro tournament of his career, defeating Onny Parun convincingly.
Also proof of his skills and success on the grass-courts down under. To underline this success he travels to Australia again in late 1974 although Borg has played too much and is burned-out tired for the first time. Yet, he wins on Aussie grass again winning the Adelaide-tourney again beating Parun. In the Commercial Union Masters for 1974 at Kooyong he defeats Parun, loses to World No. 2 Newcombe 7-6, 7-6 (without any breaks) and loses to the ultimate winner Vilas 7-5, 6-1 who was brilliant.
Exhausted he skips AO 1975.
Borg was leading against Ashe in the QF of Wimby 1975 when he injured himself, although he's the first to point out he might've not won anyway.
This is a great record for a 17-19-year-old against the brilliant opponents on the varied grass surfaces of the yearly 70s.
And we all know the next six years when Borg did the triple channel-slam, which burdened him, yet he almost did the channel slam 4-5 times if he had played RG 1977 and slammed Mac's 2nd serve on the 4th set point in the 1981 Wimby-final, for a for a typical FH-winner, going up 2 sets to 1 there. Would Mac mount a new 1980 comeback if that was the case? Maybe.
Be that as it may.
To surpass Borg a player must win his first Wimbledon at 19 or 20, without set-loss of course, against an opponent who also did not lose a set coming into final. Borg had lost to Nastase 4 times in a row starting at the Masters-final 1975 and the Wimby-final 1976 turned everything around in their H2H. After that the challenger must win 6 titles in a row and also do the channel slam, at least 4 times consecutively.
Borg was asked about this in 1980, when do you think someone else will win Wimbledon-RG three times running and Borg answered: "A 100 years. No, at least 50."
46 years have now passed and the record still stands...
Borg is definite GOAT-contender on grass.
Yet, Federer is the King of Wimbledon with 12 (!) finals, 7 finals in a row -- six titles, duplicating Borg's 5 in a row, adding 2 titles to 8 and almost a 9th, which he deserved with that brilliant performance. So that is untouchable.
But grass-court prowess is not all grass-court genius, it's about winning. It's a competition.
Yet, Sampras has a strong case for Wimby-GOAT. 7 in 8 years, a triple, followed by a quadruple, never lost a final, maybe the most devastating grass game ever at his peak and super clutch. Sweetest serving-motion ever, sorry Goran. Djokovic is also super-clutch, remember 2019 and the saved USO matchpoints against Federer and defeating old Federer 3 of 3 finals like a Boss. And he has seven titles. So for sheer clutch and success Sampras and Djokovic might be the best.
There's many good arguments...