The Blue Jays right fielder hit a pair of two-run home runs to account for all the runs scored against the Boston Red Sox right-hander in his season debut on Saturday.
Fortunately for Porcello, the Red Sox offense continues to surge in the early season and it produced enough to defeat the Blue Jays 8-4, with Dustin Pedroia and Hanley Ramirez leading the way with two RBIs each.
"After the first three innings, I thought he settled in," Red Sox manager John Farrell said. "He stayed out of the plate much more consistently. He did bend but he didn't break."
Porcello (1-0) allowed seven hits and one walk while striking out seven over six innings.
"That's part of my goal every time I take the ball, especially how much we've had the use the 'pen the last couple of nights," Porcello said.
"I had to find a way to settle down and battle through it. Our offense has been doing a fantastic job. The past two days and even the Cleveland series, they've been swinging the bats great."
Toronto right-hander R.A. Dickey (1-1) allowed seven runs (six earned) in five innings on eight hits and two walks. He struck out nine with a wicked knuckleball that gave his catcher, Josh Thole, a difficult time.
"Believe it or not, it might be the best knuckleball I've seen him have," Blue Jays manager John Gibbons said. "It was everywhere. You can just tell by the catcher. It was a battle for Josh back there.
"We shot ourselves in the foot, too, with a couple of plays out there and that didn't help things. It was tough to control that thing today."
The Red Sox used two three-run innings in defeating the Blue Jays (2-4) for the second game in a row. Toronto has lost four in a row.
"I had a good one today, really good one," Dickey said. "It was the confluence of a lot of weird things going on out there today. I had a good one and it's something to be encouraged by.
"The final line is not what I would deem acceptable, but this is a time for all of us to trust the process. For me in particular, there's a lot stuff early in the season to build on early in the season we've just have to stay the course."
Bautista's first home run of the season followed Josh Donaldson's single and gave the Blue Jays a 2-0 first-inning lead.
The Red Sox scored three runs in the third.
Rusney Castillo grounded a leadoff single through the left side and Blake Swihart walked. Dickey's errant pickoff throw to second moved the runners to second and third.
Pedroia grounded out to second to score one run.
Xander Bogaerts and Travis Shaw each hit RBI doubles and Boston led 3-2.
The Blue Jays regained the lead 4-3 when Bautista hit his second home run of the game after Donaldson doubled. It was the 29th career multi-homer game for the Blue Jays right fielder.
The Red Sox tied the game 4-4 with an unearned run in the fourth.
Brock Holt reached first base with one out on a passed ball after striking out. Castillo doubled and Swihart hit a sacrifice fly to left.
"The (knuckleballs) were moving late and big movement, it makes it tough," Thole said. "If you've got one job to do and you don't do it well, it makes for a long night.
"When they keep moving like that it makes it challenging. As good of a knuckleball as he had today, it makes it frustrating."
The Red Sox had their second three-run inning of the game in the fifth.
Pedroia singled, Bogaerts walked and, with one out, Ramirez was credited with a two-run triple when his hit to right took a weird bounce over Bautista and to the wall. Ramirez scored on a passed ball.
The Red Sox scored a run against right-hander Arnold Leon in the sixth on a one-out single by Mookie Betts and a double by Pedroia.
Right-hander Koji Uehara pitched the seventh for Boston and left-hander Robbie Ross Jr. took over in the eighth.
NOTES: Toronto LHP Franklin Morales warmed up Friday but manager John Gibbons said the reliever "felt something" and was not used in the game. RHP Jesse Chavez pitched instead, allowing a grand slam to Boston INF/OF Brock Holt. The problem with Morales is not considered serious at this stage. ...Toronto 3B Josh Donaldson started as the designated hitter for the second straight game Saturday. He has a strained right calf muscle but said it feels better and he could return to the field soon. Donaldson hit the first grand slam by a Blue Jays player in a home opener on Friday. ... Boston C Christian Vazquez (elbow surgery) caught nine innings for Triple-A Pawtucket on his rehabilitation assignment Friday and was 1-for-2 with a double and two walks. ... Boston RHP Steven Wright (season debut) will start the finale of the three-game series Sunday against RHP Marco Estrada, who will be making his season debut.