Angels can’t expect young pitchers to solve all bullpen problems

The Angels have seen enough of Jordan Walden’s 98-mph fastball and improved slider; Michael Kohn’s high-octane, low-mileage repertoire; Bobby Cassevah’s heavy sinker; and Rich Thompson’s emerging cut fastball to be encouraged about their bullpen going into the off-season.

But they’ve also seen enough young players struggle after being exposed to big league competition to know they can’t look at these young relievers and think the Angels’ bullpen problems are solved.

“The arms are there, the stuff is there, but you have to have the ability to make pitches when it counts,” Angels pitching coach Mike Butcher said. “We need to slow the game down, make pitches and stop the bleeding. The pieces are there, but a larger sample size will be to see these guys in a whole season.”

Walden, 22, has the most upside of the group. The 6-foot-5, 220-pound right-hander has a 2.25 earned-run average with 15 strikeouts and two walks in eight innings and has gained the trust of Manager Mike Scioscia, who has been using Walden in a setup role.

Kohn, 24, is the most intriguing of the bunch. He was an infielder until 2008 when, “as a joke one day” as a senior at College of Charleston (S.C.), he threw off a mound for his coach. The 96-mph readings on the radar gun were no joke.

Based on the 10 innings Kohn threw that season, the Angels drafted him in the 13th round, and the right-hander rocketed through the farm system before being called up in late July.

“I guess I was fortunate enough to pick it up quickly, and I was in the right place at the right time,” Kohn said. “But I still have a lot to learn. Most guys have me beat by 12 years’ pitching experience.”

He has a 2.51 ERA in 17 mostly low-impact appearances and has shown a 92-mph fastball. The Angels saw him hit 95 mph last season, though.

“He has a real live fastball that he hasn’t really shown this year,” Scioscia said. “He’s a guy who can definitely pitch at the back end of a bullpen when he develops.”

Cassevah, 25, who has a 4.50 ERA in nine games, led the minor leagues in ground-ball outs last season and, with his ability to throw multiple innings, is a strong long-relief candidate for 2011.

Thompson, 26, who has shuttled between triple A and the big leagues for four years, has been much more effective -- a 1.15 ERA in 10 appearances -- since adding his cutter.

“We loved his arm a couple of years ago, but he got stale, stagnant and wasn’t improving,” Scioscia said. “He’s redefined himself in the last year. He came up with a cutter, he has a good downhill angle and he’s throwing strikes. He’s pitched well in some pressure situations.”

The Angels have two hard-throwing right-handers at the back of the bullpen in closer Fernando Rodney and Kevin Jepsen, while right-hander Francisco Rodriguez has emerged as a middle-relief mainstay, with a 4.36 ERA in 39 games.

But Rodriguez is also an example of why the Angels must proceed with caution with their young relievers. Rodriguez had a 3.26 ERA on July 28 but has been roughed up several times since.

“The bottom line with some of the young guys is they have to show they can do it on a consistent basis and be able to adapt to major league hitters and scouting,” Butcher said. “I’m encouraged, but there’s a lot of work that needs to be done.”

mike.digiovanna@latimes.com