As the Red Sox notched their sixth win in seven games, Lackey posted the fourth straight outing that he's gone at least seven innings and given up two runs or fewer.
His resurgence has been a big reason why the Red Sox, despite the injuries of Clay Buchholz and the struggles of Jon Lester, have been able to maintain their position atop the American League East.
What spurred the turnaround? For Lackey, the answer is simple.
"I'm healthy," he said.
Staying healthy has certainly been an issue for Lackey since he arrived in Boston in 2010, and he had to miss the entire 2012 season while recovering from Tommy John surgery. But he rebuilt his body during the recovery and is now reaping the benefits.
"There's been a lot of hard work," he said. "Eighteen months of rehab and working in between starts. You know, my arm feels pretty good right now and it's fun to let it loose a little bit and not feel anything."
When Lackey has let loose this season, he's been able to find an extra gear. The velocity on his fastball has increased throughout the year and topped out at 96 mph Tuesday. In the first inning, he struck out the first two batters he faced on seven pitches and needed just three more to retire the side. All 10 offerings were fastballs over 92 mph.
"Establishing a fastball is always a good thing," Lackey said. "You don't want to show too much too early so you can mix things up when things get hot, guys get on base and you get in some tough situations, because pretty much every game you're going to have a situation that can kind of turn the game one way or another. To be able to mix things up in those situations when you haven't showed a whole lot is nice."
On Tuesday, that situation came in the fifth. Nick Hundley led off with a double and Alexi Amarista followed with a single to put runners on the corners with no outs. But Lackey bore down, mixed up his pitches and none of the next three batters hit the ball out of the infield.
"That's as good as I've seen John throw in a number of years," Padres manager Bud Black said. "The velocity was really up the first 50 or 60 pitches. He had a good breaking ball in the last few innings. His arm looked good."
Lackey's one blemish came in the seventh when Jesus Guzman deposited a 2-2 curveball into the Green Monster seats for his fourth home run. Lackey threw 73 strikes in 103 pitches in what was his longest outing since June 17, 2011. His 2.81 ERA is eighth in the AL.
"Once again, very good command, a lot of strikes. An outstanding performance on his part," manager John Farrell said. "All this is based on the work that John has put in and it's great to see it taking place."
Playing in his third game of the season, third baseman Brandon Snyder delivered the big blow for the Red Sox on offense. With one out and the bases loaded in the fourth, he stung the ninth pitch of his at-bat against Padres starter Robbie Erlin high off the wall in left field for a bases-clearing double. He was thrown out trying to stretch it into a triple, but as he jogged toward the dugout, the 36,498 fans at Fenway Park made it clear all was forgiven.
Snyder, who was brought up to replace the struggling Will Middlebrooks, also had a two-run double in Boston's 5-4 win over the Blue Jays on Sunday.
"It's one of those things where I've had a lot of opportunities in the past," Snyder said. "I've taken advantage of them, but I've also squandered a few. It's one of those things where you've just got to take them when you can. This game will chew you up and spit you out really quick, and it's very quick. I'm almost in my 10th year and it feels like just yesterday I signed, so anytime you get a chance to come in and try to make a difference, try to do the best you can, hopefully it works out."
David Ortiz clubbed the 500th double of his career in the first. Dustin Pedroia tried to score from first but was tagged out at the plate after a perfect relay throw from second baseman Logan Forsythe.
The Red Sox added their final run in the sixth inning when Jose Iglesias, who went 2-for-3 to raise his average to .415, grounded a ball up the middle to score Jonny Gomes.
The night was about Lackey, though. When he walked off the mound after completing his eighth inning of work, the fans at Fenway -- with whom he's had a tenuous relationship throughout the years -- rose to their feet and gave him a big ovation.
When asked if it felt good to have the fans embrace him, Lackey paused.
"I'm going out and pitching and pitching well. I guess that's all I want to see, so hopefully that's enough [for them]," he said.