"You try to put that out of your mind," the Toronto Blue Jays left-hander said. "But after being in that dugout for four months, it felt a little different facing those guys.
It did not stop Happ (13-3) from doing what he has done all season and that is winning. He held the Mariners to one hit over six innings and Edwin Encarnacion hit his 27th homer of the season to lead the Blue Jays to a 2-0 victory on Sunday afternoon.
The 13 wins are a career high for Happ for one season. He had won 12 games in 2009.
"It means a lot," Happ said. "It's a testament to our team."
The Blue Jays (55-44) averted a three-game sweep at the hands of the Mariners (50-48) by winning the finale.
"It was a really big win, especially after yesterday," Blue Jays catcher Josh Thole said, referring to Seattle's 14-5 victory on Saturday
Happ walked four batters and hit a batter besides yielding the one hit. The left-hander struck out six before being replaced by left-hander Brett Cecil to open the seventh.
Cecil pitched around a walk in his inning, striking out two. Right-hander Roberto Osuna pitched the ninth to earn his 20th save of the season.
The Blue Jays outhit the Mariners 4-1 in the game.
"Happ was certainly on," Mariners manager Scott Servais said. "He's having a good year and I can see why."
The Mariners traded Happ to the Pittsburgh Pirates last July 31.
"I thought he was a little off early in the game," Blue Jays manager John Gibbons said. "I thought he got better as the game went on. You could tell he's a different pitcher because there were a lot of guys (on the Mariners) who have hit him pretty well in the past and he shut them down pretty good today.
"He has 13 now and there's two months left, there's no telling how many he can chalk up. Probably all over baseball there probably hasn't been a more consistent starter out there. He's a better pitcher than he's ever been."
Seattle starter Wade Miley (6-8) allowed four hits, two walks and two runs in six innings. The left-hander struck out four and was replaced by right-hander Tom Wilhelmsen, who pitched a perfect seventh.
"I thought Wade Miley threw the ball very well," Servais said. "He made a mistake on the home run ball. Other than that it was a well-pitched game. There weren't a lot of opportunities but in a game like that, you've got to take advantage of them."
Said Miley: "I felt like I wasn't quite as sharp as in my last outing but I was able to make some pitches and get out of most of the jams."
"(Happ) did a great job today," Mariners catcher Mike Zunino said. "He kept the ball down in the zone, he stayed on the corners and make some big pitches when he needed to. We had some good at-bats but he did enough to keep us off the board."
With two outs in the bottom of the fourth, Encarnacion lined an 0-1 fastball to center to give Toronto the lead. He has 87 RBIs to lead the majors.
It was his 224th homer as a member of the Blue Jays to move him into third place on the club's all-time list.
Encarnacion made a diving play at first base in the fifth to deprive Leonys Martin of a hit.
Thole, playing his third straight game because Russell Martin injured his knee in a shower accident, led off the bottom of the sixth with a double. He slid in safely to third on Darwin Barney's fielder's choice grounder to first and scored when Josh Donaldson grounded into a double play to make the score 2-0.
Right-hander Jason Grilli entered the game in the eighth for Toronto. Grilli got through the inning without allowing a baserunner with some help from a diving catch by Barney on Norichika Aoki's slicing drive to third. Barney was playing third base in place of Donaldson, who was used as designated hitter.
Joaquin Benoit pitched a 1-2-3 bottom of the eighth for Seattle.
NOTES: Toronto designated RHP Drew Storen for assignment Sunday and recalled RHP Ryan Tepera from Triple-A Buffalo. Storen was 1-3 with a 6.21 ERA and three saves in 38 relief appearances. In five games with Toronto, Tepera is 0-1 with a 5.79 ERA. ... Seattle OF Franklin Gutierrez (neck) was scratched from the lineup Sunday because of a sore neck but he is expected to be available Tuesday in Pittsburgh following the Mariners' off day on Monday. ... The Mariners are scheduled to start RHP Felix Hernandez (4-4, 3.23 ERA) on Tuesday against Pirates LHP Francisco Liriano (6-9, 4.96 ERA) in the opener or a two-game set at Pittsburgh. ... Blue Jays RHP Aaron Sanchez (10-1, 2.87 ERA) will face San Diego Padres RHP Colin Rea (5-4, 5.01) in the opener of a three-game series at Rogers Centre.