The difference is so stark that attention must be paid, but it's hard to say just how much reflected glow Pirates rookie catcher Ronny Paulino should get for the way the pitchers have thrown to him.

It's just undeniable that the results have been much better when Paulino, 25, has been behind the plate.

There isn't much good you can say about the 1-6 homestand, except that the starting pitching once again kept the Pirates in most games, and Paulino was catching when they did.

The earned run average of Pirates pitchers when Paulino catches has been 3.52 this season. That's the best mark in baseball for a regular catcher.

The ERA when Humberto Cota catches is nearly twice as high at 6.88, the worst number in baseball among those who have caught at least 150 innings. Ryan Doumit's 5.74 ERA in more than 63 innings isn't much better.

That's quite a discrepancy, though, for a while, an analyst could write that off by noting that Cota and Doumit were catching mostly at the season's start, when a young rotation was settling in. Cota also had to catch the skittish Oliver Perez while Paulino did not.

But now Paulino has caught Perez six times, and Perez's ERA is 2.87 in those games, with an average of more than six innings per start. In the eight games that Cota caught Perez, the ERA had been 9.34 with an average of less than four innings per start.

Paulino seems to have aced the Perez test. So is a catcher's ERA a legitimate stat?

You'd think it would be. Some pitchers obviously believe they perform better with certain catchers; a personal backstop has been a perk of pitching stardom for decades, from Steve Carlton's Tim McCarver to Randy Johnson's John Flaherty.

But Keith Woolner of Baseball Prospectus studied the issue, and he told the New York Times last winter that a low catcher's ERA is not something that holds from year to year, which surprised him.

"This is an exaggeration," Woolner said, "but compared to the batters and the pitchers, the catcher is just a guy who makes sure the ball doesn't go to the backstop."

Even if the Paulino effect is some passing mirage, the results are startling. The Pirates' pitching staff ranked 11th in the National League through Sunday, but, for the 44 games Paulino has caught, the ERA of 3.52 would put the staff at the top of the league. Even the New York Mets of Pedro Martinez and Tom Glavine have a staff ERA of 3.84.

OK, 44 games is a small sample, and Paulino isn't entirely polished. He has six errors, second most among major-league catchers. He has four passed balls, which puts him in a six-way tie for sixth worst once the poor saps who have tried to catch Tim Wakefield's knuckleball are eliminated.

That said, all Paulino's passed balls and half his errors came in his first 14 games. He has settled considerably since. Though runs that score on passed balls and errors aren't earned, his wouldn't be enough to affect ERA dramatically.

Paulino must take part of the blame for the Pirates being tied for fourth in the league in wild pitches, as great catchers help to stop those. But runs scored on wild pitches are earned, and they clearly haven't harmed Paulino's hurlers too much.

At this point, you almost have to look at his blemishes and ask, so what? The other elements of Paulino's game are so good. Paulino has caught 17 runners stealing, the most in the National League. His caught-stealing percentage of .447 (17 in 38 attempts) is second to the St. Louis Cardinals' Yadier Molina.

It should be added that Doumit is up there with Paulino at .444 (four caught stealing in nine attempts) and Cota's .294 (five in 17 attempts) is also above the league average of .276. The team's overall mark of 41 percent tops the NL.

Barring injury, we're unlikely to find out if the pitching improvement under Paulino is some freakish coincidence. There is no reason to play anyone else.

I still like Doumit as a catcher, but he is out with a hamstring pull. Cota is hitting .213. That leaves Paulino, who has been hitting the way Jason Kendall wishes he still could.

Paulino has a .315 batting average, a .366 on-base average and a .405 slugging average. His on-base plus slugging average of .771 would have had him fourth among NL catchers through yesterday afternoon.

He's a long shot for rookie of the year. Marlins second baseman Dan Uggla (.314, 12 HRs, 42 RBIs), Brewers first baseman Prince Fielder (.296, 13, 39) and others remain well ahead. Paulino ranks seventh in OPS among rookies with at least 175 plate appearances, but his hitting has improved in each successive month. There isn't much not to like.