Bobby Valentine Warns Carlos Beltran, Fix The Mets' Bullpen!

Carlos Beltran, listen up ... Bobby Valentine's got some Mets advice, telling TMZ Sports if the new NY manager wants to win now -- FIX THE BULLPEN ASAP!!!

The Mets were a disaster at the end of games last season -- closer Edwin Diaz blew SEVEN saves -- and that ultimately led to Mickey Callaway's firing last month.

When we got Valentine out at Mariano Rivera's charity event in NYC ... the ex-Mets manager told us if Beltran wants to avoid the same fate, clean that part of NY's roster up NOW!!!

Of course, Bobby V also said it'd be great for Beltran if he could get some contributions from Yoenis Cespedes and add a little more firepower to the offense too.

"I'm pulling for him," Bobby says.

As for if Valentine thinks Beltran has the goods to eventually get the Mets back to the playoffs ... Bobby told us yes, saying, "He gets it. He's a real smooth guy."