Dickey (2-3) allowed six hits and struck out five against New York, which absorbed its second consecutive loss since coming home from an eventful road trip. A couple of Mets lost their tempers, too, as new manager Jerry Manuel and slugger Carlos Beltran were ejected for arguing balls and strikes.
Manuel was promoted from bench coach to replace fired manager Willie Randolph last week, and the Mets responded by winning series at the Los Angeles Angels and Colorado. They sent ace Johan Santana to the mound Monday night looking to build some momentum against Seattle, mired in last place in the AL West.
But Santana served up a grand slam to Felix Hernandez - the first by an American League pitcher in 37 years - and the Mets lost 5-2. Perez then followed with a typically erratic outing in the second game.
"He's tough to figure out for a manager," Manuel said before the game. "I'll be honest with you. I mean, he's tough for me to figure out."
Johjima, who entered with a .218 batting average, hit a 2-1 pitch from Perez into the visitors' bullpen in left to give Seattle a 5-0 lead in the third inning. Johjima's two-out drive was his third of the year and scored Sexson, who was aboard after a one-out single.
Perez (5-5) struck out Willie Bloomquist to get out of the inning, and the Shea Stadium crowd booed as the left-hander made his way to the dugout.
Perez allowed six runs, five earned, and seven hits in five innings. He is 1-2 with a 6.75 ERA in his last seven starts.
Sexson hit sacrifice flies in the first and sixth, then doubled in a run in the ninth. The big first baseman, who entered with a .210 average, went 2-for-3.
After taking consecutive called strikes to begin the fourth, Beltran started talking to plate umpire Brian Runge, who took off his mask and continued the dialogue before he brushed dirt off home plate. Manuel then came out and started arguing. Runge appeared to bump into the manager before throwing him out of the game.
Manuel walked to the bench as the crowd roared. Beltran continued the conversation and Runge quickly tossed him, too. An incensed Beltran then got in Runge's face and had to be held back before Manuel came out to escort him to the dugout.
Mark Lowe replaced Dickey in the eighth and got six outs to complete the eight-hitter, Seattle's fourth shutout this season.
The Mets were blanked for the second time.
New York played without All-Star third baseman David Wright, who got a rare day off. Wright was the only major leaguer to play every inning this season, though he made one start as a designated hitter.
