Kei Nishikori retired from his first match at the Barcelona Open on Wednesday just three days after contesting an ATP Masters Series final with world No. 1 Rafael Nadal.
Having received a first-round bye, Nishikori lost his second-round match to Spain's Guillermo Garcia-Lopez 6-3, 0-0 when he retired after the first set.
"I felt pain in three different parts of my body while warming up, and wasn't able to perform to my best," Nishikori said. "The biggest thing was my right calf. It rapidly got worse and I was unable to move."
The 14th-seeded Nishikori struggled with his serve and was unable to do much with his opponent's. He fended off six break points before Garcia-Lopez won the seventh game.
Nishikori didn't take a point off the Spaniard's first serve until the eighth game, but it was not enough for him to break back.
Garcia-Lopez, ranked 69th in the world, then broke the 22nd-ranked Nishikori, who then retired.
Nishikori won the Barcelona Open in 2014 and 2015, and was runner-up in 2016. The former world No. 4 prematurely ended his 2017 season last August after suffering a right wrist injury.
"If I rest, I think it will get better," Nishikori said.
He was unable to grab his first career masters championship on Sunday, losing the Monte Carlo Masters final 6-3, 6-2 to Nadal.