Keith Hernandez was missing something when he went to work on Saturday night — the right shirt.

Before the Mets’ 13-2 blowout win over the St. Louis Cardinals at Busch Stadium, Steve Cohen explained why Hernandez, who played for both teams during his illustrious MLB career, wasn’t wearing his WPIX collared shirt.

“Before we talk about the game tonight, we’ve got to talk about the elephant in the room, Keith’s shirt, you know we haven’t been on PIX 11 in a couple of weeks, so I know you that your PIX 11 shirt is not in the laundry. What happened?” Cohen asked.

“And I was telling everyone remember we got two games in St. Louis,” Hernandez said. “You got to bring your PIX shirts and what do I do, I leave it in my hotel room.

“And, I’m just a dunderhead. It’s the second time I’ve done it in 18 years.” Hernandez said and then playfully banged his microphone against his head a couple of times.

Cohen assured the viewers the collared shirt was being retrieved, and Hernandez was wearing it later in the game.

But before Hernandez’s official WPIX shirt arrived, stage manager Nancy Smith made a makeshift WPIX 11 logo that was on is shirt, which drew a chuckle from the Mets’ longtime analyst.

In Hernandez’s defense, Cohen and Hernandez — often with Ron Darling — also call the Mets’ games on SNY, which airs most of the team’s games.

Plus, the Mets have been on three different networks in the first three games of the four-game set. The opener of the series was on Fox on Thursday and the second game aired Friday on SNY.

Hernandez’s shirt snafu didn’t jinx the Mets, who have been playing better baseball recently since being trade-deadline sellers. They have won four in a row and six of seven games after Saturday night’s impressive win.

The Mets will attempt to pull of a four-game sweep of St. Louis on Sunday, and the game also will be televised on WPIX 11, so Hernandez will get a chance at some shirt redemption.