SAN DIEGO -- With three weeks left in Spring Training, Padres general manager Kevin Towers took a look at his lot of relievers and decided it simply wasn't enough, that those arms weren't the ones he wanted to carry into the regular season.

Five games into the regular season, and after what qualifies as nearly an entire makeover, Padres relievers have the best ERA (1.69) in the National League by limiting opponents to a .196 batting average.

Yes, that same bullpen that gave Towers and manager Bud Black fits in Spring Training when quality outings from relievers were awfully hard to come by.

"The guys in our bullpen, has been outstanding," Black said before Saturday's game against the Giants at PETCO Park. "I think you look at the number of innings they have pitched and the amount of zeros they have put up, it's impressive."

This from an eight-man bullpen -- the team claimed Luis Perdomo off waivers from the Giants on Friday but he has yet to pitch -- that includes five pitchers who were not with the team at the start of Spring Training in February.

San Diego relievers have allowed three earned runs over their first 16 innings of work in 2009 and those three runs came in one inning when Edward Mujica allowed them in Wednesday's 5-2 loss to the Dodgers.

"They're putting up zero after zero after zero," Black said. "It's a great start for those guys. Coming here to a new team, getting to know catchers, coaches and teammates ... it can be a little unsettling for a lot of guys."

Mujica was acquired in the last week of Spring Training from the Indians. Duaner Sanchez was picked up after being released by the Mets. Luke Gregerson was the player to be named from the Cardinals in the Khalil Greene deal. Eulogio De La Cruz was acquired in a deal from the Marlins.

The bullpen came up big in Friday's 7-3 victory over San Francisco where Gregerson, Mujica, Sanchez and Edwin Moreno combined for one unearned run over four innings with one hit allowed in that span.

That included the tightrope Gregerson, a rookie, walked in the sixth inning when starter Shawn Hill allowed a run and left with the bases loaded and no one out. Six pitches later, the inning was over as Gregerson got a 3-2-3 double-play ball and then struck out Aaron Rowand with a nasty slider, his out pitch, to end the inning.

"Realistically, in that situation -- bases loaded and no outs-- you'll give up one run and sometimes two and be happy. Six pitches and he gets out of that jam. Pretty impressive," Black said.

The relievers have walked a combined 13 batters in those 16 innings, which is something Black needs to see change. But for now, he can't argue with the results.

"The only thing that you can look at on the negative side is the high walks from the guys. That will have to come down, which I think it will," Black said. "But they've done a nice job."

Black hasn't been afraid to lean on these relievers, either. Mujica, Moreno and Gregerson have each appeared in three of the first five games. Closer Heath Bell, Sanchez and Cla Meredith have each pitched in two games.