Laver had some wrist problems that contributed to his five-set loss at the '68 USO to Cliff Drysdale. Don't know whether he still had these problems in the 70s, but here's a report on the Drysdale match, from the New York Times.
Laver lost 4-6, 6-4, 3-6, 6-1, 6-1 in the R16.
Yesterday, Laver’s normally strong serve deserted him. He faulted 79 of 139 first serves, a 43 per cent first-service ratio and hardly a statistic worthy of a Wimbledon champion.....
Drysdale’s chances improved as Laver’s first serve deteriorated. In the first three sets, he managed 43 of 93 first serves. But in the fourth set, he missed 14 of 18 and in the fifth set 15 of 28....
His 14th double-fault of the match came at deuce in the final game. Drysdale won the match with a forehand return of service placement down the line.
“My serve was the shot that let me down the whole tournament,” said Laver, who has lost four straight tournaments since returning from a vacation ordered because of persistent wrist problems. “If your confidence lets you down, you can’t do much of anything.”
Laver refused to use his ailing wrist as an alibi. But friends close to the red-haired Aussi said he has been bothered by the wrist and that complications arising from a match on Monday with Pancho Segura forced Laver to change his service grip against Drysdale.
Drysdale, 27 years old, beat Laver with consistency. Using an aluminum racquet he tried for the first time only five days ago, the South African drilled his two-handed backhand – or left-handed forehand, whichever you prefer – and concentrated on baseline play. It was an unusual strategy in an era of serve-and-volley tactics.