CHICAGO -- White Sox pitching coach Don Cooper has a simple message for those who want to kick his relievers to the curb following a bad outing or two: stop.

Through the first three-plus weeks of the season, the chorus clamoring for change in the bullpen was loud and large, but thankfully, not in charge. If it was, the White Sox bullpen never would have had the chance to stage its remarkable turnaround.

"We like our guys, we're going to continue to like our guys, we're going to continue to support our guys and we're going to continue to believe in our guys," Cooper said. "So unlike anybody that wants to run people out of town after a bad outing or two, you might as well stop that, because that ain't going to happen.

"They're doing well. We're not where we want to be, but we're certainly heading in a much, much better direction."

Until recently, Cooper's bullpen had been on a quite a roll.

Entering Wednesday's series finale with the A's, Chicago relievers had posted a 2.68 ERA since April 26, the fourth-lowest mark in the Majors in that 17-game span. That lowered the bullpen's ERA from 5.20 to 4.16 and included a 23 1/3 scoreless-innings streak that was the longest for a White Sox bullpen since 1991.

Compare that to the first 18 games of the season, in which the bullpen had a 6.12 ERA and was 1-for-6 in save opportunities, and perhaps you can understand where the chorus for change was coming from. So what has spurred such improvement?

In 57 1/3 innings over the first 18 games, White Sox relievers walked more hitters (41) than they struck out (36) -- a rate of 6.4 walks per nine innings. A starter with that rate wouldn't last long. In the 15 games leading up to the Oakland series, the strikeout-to-walk ratio had shifted back into the green (1.96), as the 'pen struck out 45 and walked 23 in 52 innings.

"I think what I'm seeing with this bullpen is guys starting to trust their stuff," said righty Zach Putnam, who leads the team with a 1.72 ERA. "We have some guys with just lights-out stuff, and trusting it in the strike zone, not walking guys and just going right after hitters has been the biggest difference over the last couple of weeks."

The "lights-out stuff" Putnam is referring to comes mostly in the form of high-quality sinkers. The key for this group is to rack up the ground balls.

Ronald Belisario leads the crew with a robust 2.50 ground-ball rate, which measures the ratio of outs a pitcher gets on the ground vs. fly balls/line drives. Jake Petricka is next at 2.40, followed by Putnam at 2.20. Closer Matt Lindstrom's ground-ball rate is 1.56.

"These guys are power arms, but they're power sinkers, they're not power four-seam guys," Cooper said. "They can get strikeouts, but their job, and what they've always done if you check their history, is get ground balls. And that's what we want them to do."

Some have much more history in the big leagues than others, which makes for an interesting dynamic. There are the youngsters (Daniel Webb, Petricka and Putnam are all between the ages of 24-26, with less than a full season under their belt), the middle-aged crop (Belisario is 31, with four-plus years of service time, and Lindstrom, 34, is in his eighth season) and the elder statesman (Scott Downs).

"We all learn from each other," Downs said. "You're always learning in this game, especially in the bullpen, because you know the ups and downs come, and they come in a flurry if you don't try to stop the bleeding. We have fun; we do joke around a lot and we have fun down there, and that's the name of the game.

"But when push comes to shove and it comes time for somebody to get warmed up, somebody's time to pitch, it's game on. We put the jokes aside and pick it back up after."

Now in his 13th season, the veteran lefty noted that Belisario is the biggest goofball, and several of his teammates agreed. Of course, being older than everyone means Downs is going to take some good-natured ribbing from the new kids on the block.

"Every time you mention that you played for the Expos, you're going to get some cracks," Downs said with a laugh. "But I mean it's all well and good, and I have fun with it as well. I know my age, I know how long I've been around, but I still feel like I've got a lot more to do in this game."

This bullpen youth movement is emblematic of the entire team's move toward younger players, many of whom are headlining the current reshaping process. Downs said that sort of thing has rejuvenated him, to the point where it's almost impossible not to join in the fun.

For Cooper, it's nothing new. Names like Hector Santiago, Addison Reed and Sergio Santos all come to mind when thinking about young relievers who were brought up from the Minors and had their own adjustment period.

"It's one we're used to," said Cooper of the challenge of bringing along young relievers. "It's a challenge, and it's fun to try to get the young guys a good foundation so they can go on and have the career they're looking for. We take an awful lot of pride in that."

Like the bullpen's stretch of dominance, all good things must come to an end. White Sox relievers have allowed 15 earned runs in their last 22 innings, a 6.14 ERA. Righty Maikel Cleto was designated for assignment, and his replacement, Frank Francisco, has allowed four earned runs in his first 2 2/3 innings with the White Sox. As Cooper knows, the season is long and will include more than one rough patch for his relievers.

"Listen, we may not always get the job done, but I like my group, our group, because I know when they lay their arms back, they're giving us the best they got," Cooper said. "When I know they're aggressive, they're given the best they've got, I can live with any of the results."