"It still comes down to executing pitches in the bottom of the zone, and for the most part, I didn't do that tonight," Lester said.
The four-run second was sparked by three straight one-out hits -- the third being a J.T. Realmuto RBI double on a full-count pitch that put Miami up 1-0.
"They had some good at-bats," Lester said. "They had some long at-bats -- fouled some pitches off and took some good pitches. I think it was the 1-2 count to [Realmuto] where the ball could have gone either way. But he works a 3-2 count and does a good job of hitting a double there and scoring a run."
Adeiny Hechavarria followed with an RBI infield single before Marlins starter Dan Haren popped up a bunt for the second out. Dee Gordon then grounded to short and was initially ruled out on Starlin Castro's throw to first, but the play was overturned on review after Marlins manager Dan Jennings challenged.
"With Stanton, I thought I had a chance of staying in with it being a big field, but he's so big and strong that he ends up getting it out," Lester said. "It was just a bad pitch -- middle up. ... Then the one to Baker, obviously, 0-2, it can't happen. I had a plan and an idea of what I wanted to do, but I didn't execute once again."
Lester was coming off a 10-strikeout performance in his last start. He notched only four strikeouts on Wednesday.
"It wasn't one of our better nights," manager Joe Maddon said. "The back-to-back homers kind of hurt us a little bit -- put some wind in their sails. It was not one of our better games overall, and you have to file it and move on."