If I asked you who had the lowest ERA of any starting pitcher in baseball, you could likely come back with five or six good guesses. If you said Tim Lincecum or Francisco Liriano, I’d say great guess, but no. If you countered with Andy Pettitte or Adam Wainwright, I’d applaud, and say try again. Even if you said Rockies standout Ubaldo Jiminez, I’d say close, but no cigar.

If you said Mike Pelfrey, with his stingy 0.69 ERA, I’d pronounce you a superfan.

It’s Pelfrey.

All the talk about a healthy Johan Santana, and it’s Pelfrey leading the Mets out of the early-season basement and back atop the division. It’s Pelfrey leading a pitching staff with an overall 3.11 ERA, third best in baseball behind the Giants and Cardinals and more than a full point below the league average. All the hype about Ike Davis’s debut and Jose Reyes returning from injury, and all Pelfrey has done is record 1/3 of the team’s wins, along with a save in a marathon 20-inning game in St. Louis.

And he’s done it all making more than $19.5 million less than current ace Santana. Pelfrey is due just $500,000 for the 2010 season.

A note about Santana: It’s not a knock on him. He’s the ace and he’s pitching like it, currently 3-1, boasting a 2.08 ERA with 28 strikeouts. I just like to see the young, cheap guns who have been booed off the field during their careers (by myself, once) exceed expectations when they’re needed most. Sure, stats even out over a 162-game season, and Santana will likely emerge as a Cy Young candidate once again if he can stay healthy. But Pelfrey has demonstrated he can pitch in this league, and he couldn’t have chosen a better time.

Only once has Pelfrey finished a season with an ERA under 5.0, which is not the performance you’d expect from a No.9 overall draft pick. But with John Maine and Oliver Perez struggling, and after finishing Spring Training 0-4 with a 6.15 ERA, Pelfrey is emerging as a potential legit No. 2 starter.

“He had a concentrated effort this spring on his secondary pitches,” manager Jerry Manuel said, “and as the spring was winding down he started to establish the two-seamer, which is his pitch.”

Dan Warthen, who took over as pitching coach for the Rick Peterson in 2008, worked with Pelfrey on his secondary pitches and on developing his split-finger, a move that Pelfrey said has given him confidence.

“I feel like I’m a different pitcher, being able to throw the secondary stuff for strikes,” Pelfrey said. “I owe Dan Warthen a lot of credit for that split-finger. That makes all the difference in the world to me, and it’s huge for me.”

“He has great rhythm,” Manuel said. “There’s a better presence. He’s staying on top of the mound. He’s ready before the hitter’s ready.”

It’s marathon season, and it’s easy to get too excited about a fast start. But it’s certainly pertinent to point out how much Pelfrey has meant to the Mets so far, not only by picking up the slack of other struggling starters, but also by pitching deep into games (five-plus innings in four of his five starts) to preserve the bullpen.

The Mets are in the midst of a six-game winning streak that has them atop the division, and Pelfrey has played a large part in that success.

His next scheduled start is Saturday, when the Mets visit the second-place Phillies.