Rafael Nadal still has to shed some rustiness after a seven-month break from tennis as he prepares to chase a record-extending 13th French Open title.
Novak Djokovic, meanwhile, still appears to have some anger issues two weeks after getting kicked out of the US Open for unintentionally hitting a line judge in the throat with a ball in a fit of anger.
Nadal's first tournament since February ended with a 6-2 7-5 loss to Diego Schwartzman in the quarter-finals of the Rome Masters on Saturday.
That was after Djokovic earned a verbal warning for smashing his racquet on the red clay midway through a 6-3 4-6 6-3 win over German qualifier Dominik Koepfer.
Nadal, a nine-time champion in Rome, had never lost to the 15th-ranked Schwartzman in nine previous meetings but the Argentine was the better player at the 10th time of asking.
For two months during the lockdown, Nadal said, he didn't touch a tennis racquet.
"It's a completely special year, an unpredictable year," Nadal said.
"At least I played three matches."
While Nadal won his opening two matches this week in straight sets, his rustiness showed from the start against Schwartzman.
The Spaniard committed nearly twice as many unforced errors, 30 to 17, and won only 29 of 63 points on his serve - resulting in five breaks.
"Losing that many serves you can't expect to win a match," Nadal said.
"So something that I have to fix. I know how to do it."
Nadal, who chose not to play the US Open due to travel concerns amid the coronavirus pandemic, had not played a tournament since winning a title in Acapulco, Mexico.
He now has one week to regroup before he attempts to win a record-extending 13th French Open title.
The Roland Garros major starts on September 27.
"I'm going to keep working and keep practising with the right attitude and I'm going to try to give (myself) a chance to be ready," Nadal said.
Earlier on Campo Centrale, when Djokovic was broken at love to even the second set at 3-3, he reacted by breaking his racquet, earning a warning from the chair umpire.
"It's not the first nor the last racquet that I'll break in my career... Of course I'm not perfect and I'm doing my best," the top-ranked Djokovic said.
Aiming for his fifth title in Rome and a record setting 36th ATP Masters 1000 title, Djokovic's semi-final opponent will be Casper Ruud.
Norwegian Ruud eliminated local favourite Matteo Berrettini 4-6 6-3 7-6 (7-5) in a match that lasted almost three hours.
Schwartzman will next face Denis Shapovalov, who held off Grigor Dimitrov 6-2 3-6 6-2.
While fans have not been admitted to the tournament yet, Italy's sports minister said that 1000 spectators will be allowed to attend the semi-finals and finals at Foro Italico.