Andy Murray blew a 4-0 lead in the deciding set and lost to Albert Ramos-Vinolas 2-6, 6-2, 7-5 in the third round of the Monte Carlo Masters on Thursday.
The right elbow injury prompted Murray to withdraw from last month's Miami Open and he also missed Britain's recent quarterfinal loss to France in the Davis Cup. The world No. 2 committed many unforced errors, and had needed to win three consecutive games to make a comeback from a 4-5 deficit in the third set to seal victory.
The Spaniard won four games in a row before Murray, his serve misfiring, applied some late pressure.
"It was a tough first match", Murray told Sky Sports.
Three-time Grand Slam victor Wawrinka never found his touch or range and conceded match point when his backhand pass - normally one of the best shots in men's tennis - clipped the net and went out. "We'll see the shots that I chose and what I would do differently", said Murray.
"He obviously started playing better towards the end of the set".
He was broken in the first game of his first round clash with Luxembourg's Gilles Muller but the Scottish top seed recovered to win 7-5, 7-5 at Roquebrune-Cap-Martin.
Zverev will be disappointed with his showing and gifted his opponent too many cheap points, but Nadal's speed and precision was too good for the world number 20.
He will not be able to get his revenge on Federer here, since the 18-time Grand Slam champion is skipping the tournament.
Murray took his time to come to grips with the clay surface, winning his first clay title in Munich in 2015, 10 years into his professional career. "It was very tiring for me, the first clay of the season". Albert Ramos, who defeated Andy Murray on Thursday, will face Marin Cilic, who is playing much better than he did in the first quarter of the season.
"When you're coming back from not really serving for a few weeks, it's I think pretty normal to show some rust", he said. That s only going to get better. The Croatian reached the last eight after beating No 9 Tomas Berdych 6-2 7-6 (0).
Murray's enforced absence at least gave him the added bonus of spending more time with his wife and young daughter.
Wednesday's later matches saw world No.11 Grigor Dimitrov, the eighth seed, suffer an unexpected 4-6 6-3 6-2 defeat at the hands of German qualifier Jan-Lennard Struff.