Happ responded by allowing just one run over seven strong innings, but the Blue Jays' offense disappeared for long stretches and Casey Janssen eventually let things get away in the ninth en route to a 5-1 loss at Rogers Centre.
"Definitely had a heavy heart," Happ said after the game, attempting to fight off his emotions. "Tried to use it. I probably had a little bit different attitude, a little different outlook given the last few days, but I felt good. Glad to get to family this week."
Happ, who was placed on the three-day bereavement list after the game, deserved a better fate, but didn't factor into the decision due to a lack of run support.
Happ surrendered a leadoff homer to Chris Young on the 10th pitch of the first inning, but was relatively flawless from that point forward. He allowed just three hits and two walks while striking out six and throwing 78 of his 116 pitches for strikes.
It was a major step in the right direction for Happ, who was making just his second start since being activated off the 60-day disabled list. Happ had previously been out since the beginning of May after he was struck in the head by a line drive off the bat of Tampa Bay's Desmond Jennings.
Happ struggled in his return to the mound by allowing seven runs in Seattle last Wednesday, but didn't experience nearly the same amount of difficulties against the A's. He surrendered one run in the first and then had two runners on with nobody out in the second before escaping the jam without further damage.
The 30-year-old Happ recorded most of his outs through the air and didn't give up a lot of hard-hit balls while limiting Oakland to 0-for-6 with runners in scoring position. Happ finished his outing by retiring 18 of the final 20 batters he faced before a high pitch count resulted in his departure.
"This game is kind of crazy," Happ said. "The Seattle game got away from me a little bit. [Oakland] hit some hard balls today right at some guys. Sometimes, it bounces out that way. Definitely happy about that.
"Just trying to be aggressive. Just trying to throw everything aggressively."
The Blue Jays did little to provide any type of support to Happ, despite his impressive performance. Toronto roughed up Dan Straily for five runs over just 4 2/3 innings in late July, but this time around Oakland's right-hander cruised for most of the game.
Toronto put just two runners in scoring position through the first seven innings before finally catching a break in the eighth. Jose Reyes got the rally started with a one-out single to right and advanced to third on a single by Maicer Izturis.
That marked the end for Straily, as A's manager Bob Melvin opted to make a move to the bullpen. The move appeared to pay off when Ryan Cook induced a hard ground ball off the bat of Jose Bautista that should have been turned into an inning-ending double play. Instead, third baseman Alberto Callaspo had the ball go under his glove as Reyes came in to score on the error.
It spoiled what was otherwise an impressive afternoon for Straily, who allowed just the one run on six hits while striking out five. That mattered little in the end, though, as the A's went on to win for the eighth time in their past 11 games at Rogers Centre.
"I feel like we needed it, the team needed it, especially after yesterday, taxing the back end of the bullpen a little bit," Straily said. "Going into today, the mindset was throwing as hard as I can for as long as I can. I was able to execute pitches, keep the ball down in the zone, and that's something I haven't been able to do the last few times out."
The pitchers' duel between Happ and Straily was the main storyline, but it was Janssen who ended up taking a rare loss when he surrendered four runs in the top of the ninth.
Janssen entered after Toronto rallied to tie the game, but the momentum proved to be short lived. The trouble started when Janssen allowed a one-out double to Brandon Moss, which put runners on second and third with one out.
The Blue Jays then intentionally walked Josh Reddick before things fell apart with the bases loaded. Callaspo doubled in two, Stephen Vogt singled home another and Eric Sogard delivered a sacrifice fly as the A's went into cruise control and took a commanding lead.
The four earned runs are a season high for Janssen, who has converted all but two of his 23 save opportunities this season. Janssen's previous high was two earned runs allowed, which he previously had done four times this season. As a result, his ERA jumped from 2.41 to 3.32.
"They just hit him," Blue Jays manager John Gibbons said. "He's had a great year, himself. Some teams just give you trouble. He got the save the other day, but they threw out some hits. Sometimes, it's like that. Different teams, for whatever reason, hit you well. They came out swinging. They got to us the last two games late in the game."