But the veteran right-hander, who won the Cy Young Award two years ago, will use the rest of September to straighten himself out on the mound so he can help his team get where it wants to go.
Porcello, who faces the New York Mets in the second game of a three-game interleague series Saturday at Fenway Park, is 16-7 with a 4.27 ERA on the season. However, he is 2-3 with a 5.82 ERA in his last seven starts, yielding 10 home runs over that span.
Prior to that, he was 14-4 with a 3.84 ERA.
Porcello is 1-1 with an 8.44 ERA in two career starts against the Mets, but he has not faced them since 2013.
Porcello will face Mets rookie Corey Oswalt as the Red Sox look to even the series after Friday night's 8-0 Mets victory -- their fourth in a row -- which snapped Boston's four-game winning streak.
Oswalt is 3-2 with a 6.62 ERA in 14 games, nine as a starter, and he has never faced the Red Sox.
The Red Sox came into Friday night's game 35-8 in their last 43 interleague games, but the Mets hit four homers and got seven shutout innings from Noah Syndergaard for the easy win, their fourth in 48 hours. Syndergaard (12-3) gave up three hits, walked three and struck out six.
The Red Sox were set to start utility pitcher Hector Velazquez on Friday, but had to make a change as Velazquez was ill, turning it into a complete bullpen game.
Left-hander Brian Johnson, fighting for a postseason spot, wound up going 4 2/3 innings and allowing only one run -- on one of the four New York homers.
"He threw the ball better," said Boston manager Alex Cora. "When he came in with the bases loaded one thing was different from the last one. I was like, 'Hey man, slow down.' That's the most important thing. You have to throw strikes, but make sure you slow down. He did a good job."
With the Boston loss and a win by the New York Yankees, the Red Sox, who have already clinched a postseason berth, saw their magic number for wrapping up the American League East remain at six.
The "highlight" of the game for the local fans was the sight of a couple of rats, one very large, in and near the Mets dugout, providing some comic relief and plenty of finger pointing.
"The thing was, he was a nice rat," said New York's Dominic Smith, who recently watched a documentary about rats. "He wasn't trying to get anybody. He was trying to run. There are some mean rats out there."
Reliever Matt Barnes, a favorite in the Red Sox's eighth-inning setup picture but out with hip inflammation, returned to a mound for the first time in almost a week with a side session.
"Everything went well," Cora said. "We'll see how he recovers, and if everything goes fine, he'll throw another one on Sunday."
Eduardo Nunez was out of the lineup Friday with a sore knee and won't play Saturday, either.
The Mets announced that David Wright, who is set to start at third base Sept. 29 in what will likely be his final game (because of injuries), will be used as a pinch hitter before that date.
"I need to at least give him a few-innings heads-up," manager Mickey Callaway said before Friday night's game. "We'll know how the game's going and things like that. He's definitely going to need a little time to prepare."
Veterans Jose Reyes and Jose Lobaton are the only current Mets with significant at-bats against Porcello. Reyes is 6-for-12 (.500) and Lobaton 3-for-8 (.375).
Jacob deGrom and Chris Sale are matched up in a duel of aces Sunday, but that's a bit misleading because Sale, who is still rebounding from left shoulder inflammation, is only slated to pitch three innings as the "opener."