NEW YORK -- When Kaz Ishii became the latest Mets starter to land on the disabled list, manager Willie Randolph knew who he would turn to.
"We didn't have a whole lot of options," Randolph said.
Jae Seo pitched six sharp innings after being called up from the minors earlier in the day, and rookie Victor Diaz had his first four-hit game to lead New York over the Washington Nationals 10-5 Saturday.
The Mets scored all their runs in the fourth and fifth, batting around in both innings. New York has won 10 of 13 since opening the season with five straight losses.
Ishii went on the disabled list Friday night with a strained muscle in his side. With Kris Benson (strained chest muscle) and Steve Trachsel (herniated disc) also hurt, the Mets recalled Seo, who was 0-0 with an 8.22 ERA in 15 1/3 innings with Triple-A Norfolk.
Seo (1-1) allowed a run and six hits against the Nationals for his first major league win as a starter since June 29. He went 5-10 with a 4.90 ERA for the Mets last season.
"He did a nice job for us. I can't say enough for him," Randolph said. "The fact that he's had some experience -- I'm real comfortable with that."
Seo struck out four and took a shutout into the sixth before allowing an RBI single to Carlos Baerga. Pitching on short rest after throwing 4 1/3 innings for Norfolk on Tuesday, Seo was lifted after 79 pitches.
He even added a two-run single during the Mets' six-run fifth, increasing his career RBI total to three.
"There were runners on base, I was thinking I've got to get my bat on the ball," Seo said through a translator. "I was hoping for a fly ball."
Diaz went 4-for-4 with a walk, two doubles and three RBIs for the Mets. His previous career high of three hits came April 6 at Cincinnati.
Washington starter Tomo Ohka (1-3) lasted just three-plus innings in another erratic start. Diaz chased him with a two-run double in the fourth, and Chris Woodward added a two-run single off reliever Gary Majewski one out later.
Ohka was charged with all four of New York's runs in the fourth. He allowed six hits, walked three and struck out one. The right-hander has walked 15 and struck out just seven in 20 innings this season.
"He says he's fine, he's all right. My instincts tell me better," Nationals manager Frank Robinson said. "I've been around a lot. I've seen a lot of this. I'd be willing to stake a little bit of my reputation in this game ... that he's hurt."
When asked if he was hurt, Ohka conceded "a little bit."
But he wouldn't elaborate.
"I don't want to tell you," he said.
The Nationals came unglued in the fifth, when the Mets' first nine batters reached safely. With runners on second and third after David Wright's RBI double, Diaz hit a high popup to shallow right field. Second baseman Jose Vidro backed up and appeared to be under it, but on a windy day at Shea Stadium, Vidro ended up having to dive to his right and the ball fell in for an RBI double.
"I got some good pitches, and I was kind of lucky on the routine popup," said Diaz, batting .362 with three home runs and 10 RBIs in 47 at-bats.
Seo followed with a single up the middle to make it 8-0, and after Woodward's single, Baerga let Miguel Cairo's grounder to third go through his legs for an error, allowing another run to score. Carlos Beltran's double to left made it 10-0.
With runners at second and third, Baerga fielded Mike Piazza's grounder, but instead of throwing to first, he tried to beat Cairo back to third. Cairo made it back safely, and the bases were loaded, but reliever Joe Horgan struck out Cliff Floyd, Doug Mientkiewicz and Wright to end the inning.
Horgan pitched one inning, allowing six runs, five earned, and six hits.
"We have to come out here and play our best ballgame tomorrow," Robinson said. "Get ourselves a win and go home and hopefully we can get this straightened out."
The Nationals have lost five of six -- including three straight for the first time this season.
Mets reliever Dae-Sung Koo allowed three runs in the seventh. Manny Aybar pitched the eighth, and Heath Bell finished.
Washington's Nick Johnson extended his hitting streak to 13 games -- the longest in the National League this season -- with a sixth-inning single.
The Mets improved to 7-1 at home. ... Floyd went 2-for-4 to extend his hitting streak to 10 games. ... Mets SS Jose Reyes was given the day off after starting the first 17 games of the season. Woodward replaced him. ... Johnson has reached base in all 18 games.