Pedro Martinez makes his most important start as a Met tonight when he faces a Triple-A lineup from the Cubs in the finale of a four-game series at Shea Stadium. This is a must-win for Pedro with the Mets 1½ games behind the Phillies in the NL East and tied with the Brewers in the wild-card race. Jerry Manuel‘s club also is reeling, having dropped four of its past five games.

Martinez, though, doesn’t appear to have much left in the tank. He has lost his past three starts and has just one win since Aug. 16. Pedro also continues to struggle early, giving up 21 first-inning runs in his 19 starts.

Martinez will be faced by right-hander Rich Harden, who is 5-1 with a 1.66 ERA since coming over in a midseason trade with Oakland. Harden won’t have much top-line support, though, as the Cubs are resting most of their regulars.

As for the Mets, Manuel is going with Daniel Murphy in left field, Ramon Martinez at second base and Robinson Cancel behind the plate. He also is sticking with the struggling Ryan Church in right field.

The overall lineup for the 87-71 Mets:

Jose Reyes SS

Daniel Murphy LF

David Wright 3B

Carlos Delgado 1B

Carlos Beltran CF

Ryan Church RF

Ramon Martinez 2B

Robinson Cancel C

Pedro Martinez RHP (5-6, 5.60)

The 96-61 Cubs will go with:

Felix Pie LF

Ryan Theriot SS

Micah Hoffpauir 1B

Jim Edmonds CF

Mike Fontenot 2B

Casey McGehee 3B

Kosuke Fukudome RF

Koyie Hill C

Rich Harden RHP (5-1, 1.66)

Game time: 7:10 p.m.

TV: SNY.