Towers (11-10) gave up two runs and nine hits. He has lasted six innings or more in 10 straight starts, going 5-2 with a 2.41 ERA.
"I liked the way we played today," Towers said. "Everybody had good at-bats and that carries onto the field. You feel good about yourself."
Towers struck out five and walked one. He has walked two or less in 28 of 29 starts this season.
"Josh settled in and pitched good," Blue Jays manager John Gibbons said.
Koskie had a solo homer off Seth McClung (6-9) in the third and added an RBI single during a two-run seventh. The Blue Jays have only three homers in the past 14 games.
Jorge Cantu drove in his team-best 102nd run on a grounder for Tampa Bay, which had won four of five. Two of the wins came during a three-game series at Yankee Stadium that ended Thursday.
"That wasn't a very good ballgame," manager Lou Piniella said. "We came in at 3 in the morning and we played like it."
McClung allowed five runs and six hits in two-plus innings.
"He didn't have real good stuff," Piniella said. "With younger pitchers you're going to get some inconsistency."
The Devil Rays tied it at 2 in the bottom half on Cantu's RBI grounder and a run-scoring double by Aubrey Huff.
"After their first inning, we said in the dugout it looks like it has a weird vibe tonight," Towers said.
"It gives me a lot of confidence for the rest of this season and hopefully into next year," Gross said.
Koskie gave the Blue Jays a 5-2 lead with his 11th homer in the third. After Russ Adams hit an RBI double in the seventh, Koskie made it 7-2 with his run-scoring single.
The Devil Rays loaded the bases with two outs in the second, but failed to score when Cantu grounded out. Tampa Bay's Carl Crawford was thrown out at the plate in the fifth by first baseman Hillenbrand when he attempted to score from second on Jonny Gomes' two-out infield single.
"We just didn't look like the team you've been seeing lately," Gathright said. "One of those games you try and forget."
Tampa Bay is 31-22 since the All-Star break.
- Six-time All-Star Bert Campaneris and former boxing world champions Alexis Arguello and Felix Trinidad threw ceremonial first pitches as part of Hispanic Heritage Night.
- Blue Jays 2B Orlando Hudson was out of the lineup because of a sprained left ankle.
- Tampa Bay bench coach John McLaren began serving a three-game suspension for his outburst during a game last week in Boston.
- The announced crowd was 10,092, giving the Devil Rays a home attendance of 967,675 in 70 dates. Tampa Bay is the only team in the majors not to reach the 1 million mark this season.
- Toronto pitching coach Brad Arnsberg, who was hit in the thumb and then the top of the head by Cantu's bat in the dugout during the eighth, said he is fine. The bat went flying out of Cantu's hands after a swinging strike. "Check the bat," Arnsberg said. "Make sure the bat's OK."