MIAMI — The Mets have stuck with Neil Walker, even through a two-month tailspin that has made him one of the least productive second basemen in baseball. But that leeway may be starting to run out.

When the Mets begin a three-game series against the Cardinals on Monday, Walker could be out of the starting lineup for the second straight day, manager Terry Collins said after Sunday’s 3-0 win over the Marlins.

“He’s struggling to the point where I think it’s more mental than physical,” Collins said of Walker, who did not play in the series finale. “He just needs a break.”

That mental-health breather could extend another day for Walker, who is hitting .089 (4-for-45) since July 4, including a 2-for-27 stretch during the Mets’ nine-game road trip.

“It’s right around the corner,” said Walker, who has struggled while the man he replaced, Daniel Murphy, has blossomed as an NL MVP candidate with the Nationals. “I feel good. Obviously, the numbers aren’t there. But my track record has always been good in July and August. More than anything, I’m healthy, which is good. I need to get back to the basics and I’ll be fine.”

Walker’s fast start to the season — he posted an .858 OPS in the first two months — helped the Mets overcome injury issues. But his downturn — he has a .544 OPS since June 1 — comes at a time when the Mets have alternatives on the bench.

advertisement | advertise on newsday

Wilmer Flores’ best defensive position may be second base. Though he has played only sporadically, with his chances coming mostly against lefties, Flores has five homers in his last nine games.

“Obviously the last couple of months have not gone the way that I’ve hoped,” Walker said. “I know I’m a lot better than what I’ve been doing.”

Extra bases

The Mets may be looking for an experienced righthanded reliever, but a source said they’re not inclined to take a shot on former Nationals closer Drew Storen, who was designated for assignment on Sunday by the Blue Jays. Storen, 28, posted a 6.21 ERA in 33 1⁄3 innings . . . Asdrubal Cabrera is hitless in his last 32 at-bats with runners in scoring position, a streak that dates to May 23.