WHAT IT MEANS: Poor Johan Santana. And this time, it didn’t get to Frank Francisco for the bullpen letdown to occur.

Cincinnati scored four runs in the eighth inning to deprive Santana of another win and leave Terry Collins’ maneuvering open to second-guessing as the Mets lost to the Reds, 6-3, Wednesday at Citi Field.

Despite Bobby Parnell requiring only five pitches to strike out Zack Cozart and strand a runner in scoring position inherited from Santana to end the seventh, Collins went with Jon Rauch to start the eighth.

Rauch proceeded to allow a leadoff single to Drew Stubbs, then double to lefty-hitting Joey Votto that put the tying and go-ahead runs in scoring position. Collins alternatively could have used Parnell to face Stubbs, then gone with southpaw Tim Byrdak to try to neutralize Votto, the lone lefty hitter in Cincinnati’s starting lineup.

(With only one southpaw in the bullpen, Collins may have been holding Byrdak back for an inevitable pinch-hit opportunity by Jay Bruce. Byrdak had struck out Bruce twice in Cincinnati last year, after serving up the walk-off homer to Bruce that clinched the NL Central title for the Reds the previous year while with the Houston Astros.)

Anyway, Rauch then surrendered a game-tying RBI single to Brandon Phillips. Byrdak eventually was brought in when Bruce entered as a pinch hitter, and Bruce delivered a go-ahead sacrifice fly to right field.

Collins, left with few remaining bullpen options given Ramon Ramirez tossed 2 2/3 innings the previous night once D.J. Carrasco was tossed for hitting Ryan Braun, went with Carrasco. He served up a first-pitch two-run homer to Toms River, N.J., native Todd Frazier.

Frazier, starting with Scott Rolen on the DL, also had homered the previous inning against Santana to pull Cincinnati within 3-2.

YO! Santana limited Cincinnati to two runs and six hits while walking two and striking out five in 6 2/3 innings.

ALMOST FAMOUS: Ike Davis snapped an 0-for-16 skid with a tiebreaking RBI double in the sixth inning and Mike Nickeas followed by becoming the second Met with a successful squeeze bunt on the brief homestand as the Mets took a 3-1 lead in the sixth.

Votto, the reigning NL Gold Glove winner at first base, committed a costly error that opened the door.

With the score tied at 1, Lucas Duda opened the half-inning with a single. Daniel Murphy then sent a hard smash to Votto, who fielded the ball while on the ground. Votto wildly threw to second, allowing Duda to advance to third and Murphy to reach safely. Davis then followed with the RBI double. And Nickeas gave the Mets the 3-1 lead by joining Ronny Cedeno as this week’s successful squeeze bunters.

WHAT’S NEXT: The Mets complete a four-game homestand as R.A. Dickey (5-1, 3.65 ERA) opposes right-hander Mat Latos (2-2, 4.54). They then don hockey apparel in a team-building exercise, grab their passports and head to Toronto for the first time since 2006.