The Mets are looking for a big year from Perez, who finished last season on the disabled list after undergoing right knee surgery September 1. He struggled with his motion all year because of his knee problems, finishing with a 3-4 record and a 6.82 ERA in 14 starts.
Perez allowed five runs and seven hits in three innings against Washington. The notoriously wild left-hander issued just one walk and struck out two.
"He threw strikes. That was the main focus we had going in," manager Jerry Manuel said. "We felt if he could get some level of comfort out there and throw strikes that we'd be very satisfied."
Washington got to Perez for three in the first, one in the second and one in the third. Mike Morse hit a two-run drive in the first for his second homer in two days against the Mets.
"I was really happy to be on the mound and start a game," Perez said. "I was a little nervous. I used all my pitches. My changeup was really good. My fastball wasn't spotted, but I felt great."
Jason Marquis, who signed a free-agent deal with Washington in the offseason, also had a rough start in his first spring game. He gave up five runs and three hits in two innings, walked three and struck out none.
Santos hit a drive into the left-field corner in the second that Willy Taveras signaled was out of play after trying to retrieve it. The umpire ruled it was in play as Santos circled the bases.
Left-hander Hisanori Takahashi, who agreed to a minor league deal with New York last month, followed Perez with three scoreless innings. He allowed one hit, struck out six and walked none.
"He was very good," Manuel said. "I had heard that he was a strike thrower, and he seems to have instincts for pitching. He'd put a little on, take a little off. I'm very excited to watch him pitch again."
MASN will broadcast Tuesday's spring debut of Washington RHP Stephen Strasburg, who was selected with the No. 1 overall pick in last year's draft. ... Nationals LHP Scott Olsen will start Monday's split-squad game in Viera against Florida ... New York OF Jeff Francoeur tossed out a pair of runners at home plate, ending the third and eighth. ... Pat Misch pitched three scoreless innings to get the save.