Ryan Doumit and Jamey Carroll added two hits apiece for the Twins, who became the last team in the majors to reach double-digit wins by splitting the four-game series. Matt Capps pitched a scoreless ninth for his seventh save in as many chances.
Diamond (2-0) has given the Twins the type of starting pitching that has been sorely lacking for most of the season. Minnesota starters entered the game with a collective 6.57 ERA, the worst in baseball.
Called up from Triple-A Rochester on Monday, he threw seven shutout innings Tuesday night against the Los Angeles Angels. Just as he did then, Diamond worked ahead in the count, moved the ball in and out and primarily kept the ball down in the zone. He allowed five hits and struck out four without a walk.
"I was getting hit hard, but our defense came up big for me," he said. "I'm not a strikeout guy, so I just want them to keep hitting the ball in play and we were able to get some outs."
Diamond was hit with a line drive on his pitching shoulder in the second inning, but he kept stretching in the dugout between innings.
Last year, Diamond was 1-5 in seven starts for the Twins. This year he's more relaxed, taking things simpler and is focusing on the batter rather than letting things get out of control.
"Taking a couple of deep breaths on the mound has got me back to settling down," he said. "This year it's more about getting back, getting wins, and helping this team out in whatever way I could."
P.J. Walters allowed two runs in six hits taking Saturday's 2-1 loss, but maybe the young guns are what the Twins need now.
"They competed in spring training, and they went down and worked on some things and we had starters here," catcher Drew Butera said. "They have major league stuff."
Toronto starter Ricky Romero (4-1) allowed nine hits in 5 1/3 innings, walked five and did not strike out a batter for the first time in 101 career starts. He threw only 51 of his 99 pitches for strikes. He has just one win in his past four outings.
"It's mechanics," he said. "I'm rushing through my delivery. I worked on it all week. This game just tests you sometimes mentally. You just got to stay mentally strong and just continue to work."
Dozier, the Twins' 2011 minor leaguer of the year who was also called up Monday, homered in the third for a 1-0 lead before the patient Twins scored three times in the fifth.
Denard Span and Dozier singled before Joe Mauer walked to load the bases with no outs. Josh Willingham walked and Doumit followed with a two-run single up the middle. It was Minnesota's only hit with runners in scoring position over its past 19 opportunities.
"We faced a very good pitcher, Romero's going to make you work," said Minnesota manager Ron Gardenhire. "We made him work pretty hard and we got his pitch, so it says a lot about the way we had at-bats, we made him throw pitches, but we couldn't finish him off. We had an opportunity to open it up."
That lack of timely hitting nearly cost the Twins as Toronto scored three times in the eighth inning.
"We got a bunch of fighters. We don't give up until the last out," Davis said. "Unfortunately we came up on the wrong side."
The rough start has put Minnesota in a deep hole early, but Dozier isn't concerned.
"We're playing good baseball right now," Dozier said. "We'll get things going."
Toronto turned two double plays for a league-best 45. ... Davis had two of Toronto's four stolen bases. ... Minnesota's Trevor Plouffe ended a 0-for-11 skid with a seventh-inning double. ... Minnesota opens a two-game homestand against Cleveland on Monday. Carl Pavano (2-3, 5.02 ERA) will take the hill for the Twins against Jeanmar Gomez (2-2, 4.66). Pavano said Sunday he recently had an MRI that revealed a strained shoulder, but that he's good for Monday. ... Brandon Morrow (4-1, 2.27) is scheduled to start Monday when the Blue Jays return home to face Tampa Bay and Jeff Niemann (2-3, 3.48).