PORT ST. LUCIE — Jose Valentin’s comeback is officially ahead of schedule. The veteran infielder, who is in camp on a minor-league contract because the Mets weren’t sure if he would recover from reconstructive knee surgery, is making a surprise appearance in the lineup here today against the Astros.

Valentin, a key piece in the Mets’ 2006 run to the NLCS, will start at first base. He’s only played three innings in his 14-year career there, but the Mets have a big hole at first with Carlos Delgado’s continued absence due to a hip ailment.

Valentin’s right knee was in such bad shape that he had to have a cadaver ligament inserted. The Mets originally thought Valentin wouldn’t be ready until at least May, if at all.