Seattle handed Porcello his first loss since May 17, snapping a streak of eight straight wins by the Boston right-hander. Porcello (14-3) had allowed one home run in his previous seven starts before losing on three solo homers in a ballpark known for not yielding the long ball.
"It doesn't happen very often where you feel like you're throwing the ball well but you give up three home runs. It's just kind of one of those things I can't really explain right now," Porcello said. "They did a good job."
Cruz hit his 27th homer of the season leading off the second inning, Zunino hit his fifth leading off the sixth and Lind capped Seattle's scoring with his 16th of the season with two outs in the seventh. They were the only three hits allowed by Porcello until Zunino's single in the eighth.
The three home runs by Seattle accounted for the only three costly mistakes Porcello made in an otherwise strong start. Cruz's homer was estimated at 441 feet and reached the second deck in left field. Zunino's traveled 427 feet to center on a night when swirling wind appeared to be knocking down fly balls to that part of the outfield. And Lind kept his fly ball fair down the right-field line to give Seattle a 3-0 lead.
Porcello struck out eight and walked one.
"He made a couple of mistakes and we got on him," Seattle manager Scott Servais said. "Big night by Zunino. That is big-time power to go out of the park in that spot there."
Iwakuma (12-7) rebounded from a season-worst performance against the Chicago Cubs to limit Boston to five hits, a team that had given him problems in the past. In five previous starts against the Red Sox, Iwakuma had allowed 21 earned runs in 22 innings.
He was dominant from the start this time, striking out four of his first five batters. Only one runner reached second base in the first seven innings against Iwakuma. Top prospect Andrew Benintendi got his first major league hit in the third and advanced to second on Brock Holt's two-out single. Benintendi was stranded when Xander Bogaerts fouled out.
Iwakuma struck out seven and walked none, leaving in the eighth after Benintendi's second hit. Mookie Betts greeted reliever Drew Storen with a single to advance Benintendi to second, but he was stranded there again after Bogaerts flied out to the warning track in left.
"I was able to command my fastball, and my fastball I think had more life than usual," Iwakuma said through a translator.