Walker won as a starter for the first time since 2002 and the Blue Jays beat the Baltimore Orioles 3-2 Wednesday night.
Walker (3-0) pitched in Japan last year and was effective as a long reliever this season before being inserted into the rotation because David Bush and Chad Gaudin were struggling. Walker allowed two runs and five hits in 5 1/3 innings for his first win as a starter since Sept. 27, 2002, against Detroit. He struck out three and walked none.
"I enjoyed being out there. I like starting, but I also was comfortable down in the pen doing what I was doing," said Walker, who has a 1.51 ERA.
Walker threw 75 pitches. He's expected to remain in the rotation until at least the All-Star break.
"He gave us a big boost. He threw a lot of pitches for what he's been doing this year," Toronto manager John Gibbons said. "It was just a big win."
Baltimore's Larry Bigbie gave Walker credit.
"You have to tip your hat," Bigbie said. "He used both sides of the plate, had movement on his pitches and kept us off-balance."
Baltimore's Rafael Palmeiro hit his 561st career homer, two from tying Reggie Jackson for ninth on the all-time list. Palmeiro is also 17 hits shy of 3000.
Miguel Batista pitched 1 2/3 innings for his 13th save as the Blue Jays moved back to .500 (36-36) and are in fourth place, 6½ games behind the first-place Orioles.
Orioles third baseman Melvin Mora missed the game with a strained right hamstring and is listed as day to day.
"It's too early to tell when he's going to be back," trainer Richie Bancells said.
Baltimore starter Daniel Cabrera (5-7) lost his third straight start, allowing three runs on five hits in five innings. He struck out seven and walked three. He threw 100 pitches, 62 for strikes.
"He got his pitch count up high too early," Baltimore manager Lee Mazzilli said. "He had 100 pitches in the fifth inning. I wanted him to go deeper but he just couldn't do it."
Gibbons said Cabrera has the best young arm in baseball.
"You try to hit a 98 mph fastball, and a 85, 86 mph hook, it's not easy," Gibbons said. "He battled, but we got the big break with the balk."
Bigbie singled in the third and scored on Brian Roberts' RBI double.
Gabe Gross led off Toronto's third with a triple and scored on Orlando Hudson's RBI grounder to tie it 1-all.
Palmeiro gave Baltimore a 2-1 lead in the fourth his 10th homer of the season.
But Shea Hillenbrand hit an RBI grounder in the fifth, and Russ Adams scored on Cabrera's run-scoring balk to make it 3-2.
- The Orioles placed OF B.J. Surhoff on the 15-day disabled list with a strained muscle above his ribcage, and recalled outfielder David Newhan from Triple-A Ottawa. Newhan is back up after getting sent down Sunday when Luis Matos was activated off the DL. In 40 games with the Orioles, he hit .194 with three homers and 12 RBI.
- Hill had 40 hits in his first 30 games, tying him with Al Woods (1977) for the most in club history after 30 games.
- Toronto's Hudson robbed Jay Gibbons with a diving stop on a grounder in the ninth.