MILWAUKEE -- The way Brewers manager Ned Yost sees it, his bullpen had a bad night Friday but is not in need of retooling for the second half.

"Our bullpen guys are doing exactly what we're asking them to do," Yost said Saturday, a day after Brewers relievers combined to surrender four runs in Friday's 7-2 loss to the Cubs. "The results weren't there, but they weren't horrible."

Before Rick Helling blanked the Cubs over the final 1 1/3 innings, three Brewers relievers combined to surrender four Cubs runs on six hits over 2 1/3 innings. For the season, the Brewers lead the National League with 19 relief wins, but the bullpen's 5.15 ERA was second-worst only to the struggling Cincinnati Reds' 5.16.

The three relievers at the back end of Milwaukee's bullpen have particularly struggled. Dan Kolb has an 18.00 ERA over his last nine appearances. Matt Wise has a 10.13 ERA over his last nine appearances. Closer Derrick Turnbow has a 31.50 ERA over his last three outings and is 11-for-17 in save opportunities since converting each of his first 12.

On Friday, the most damage was done against Kolb, the former Brewers All-Star closer reacquired this season to serve as a setup man. He surrendered a pair of ground-ball singles leading off the eighth inning and was removed after a sacrifice bunt. Both Cubs runs scored against reliever Brian Shouse.

"Danny's alright," Yost said. "He had a good outing [on Wednesday]. You ask your bullpen guys to come in and get ground balls. He got two ground balls [Friday] night. They're finding holes right now.

"That's the difference. When you're not going good, you're giving up homers, doubles, line drives. When you're pitching OK and things aren't really that bad, you're giving up ground balls -- you're doing your job -- but they're finding holes. There's a huge difference in results. You just don't look at, 'He gave up two hits and the world's caving in.'"

The bright spot Friday was Helling, who has surrendered one earned run in three appearances since moving from the starting rotation to the bullpen.

Still out: Corey Koskie remained sidelined Saturday with what is now being called a slight concussion. The veteran third baseman has felt dizzy since falling backwards on a wild defensive play in the seventh inning Wednesday night.

"He's still dizzy," Yost said. "We can use him to pinch-hit."

Koskie felt dizzy and slightly nauseated after combining with Bill Hall on a highlight-worthy play in the Brewers' win over the Reds. He skipped batting practice on Saturday, and Yost said he would rest Koskie through next week's All-Star break.

Koskie, who grew up playing hockey in Manitoba, believes this is his first concussion.

"I don't know for sure, though," he said. "I've gotten hit in the face by pucks. You'll feel dizzy for a while, but nothing was ever diagnosed."

He's feeling better every day.

"The pressure in my head is gone," Koskie said. "The first couple days, there was a lot of pressure all through there."

Back in the bigs: Mike Rivera came full circle on Friday night.

The 29-year-old catcher started behind the plate in his first Major League game since May 20, 2003, when he went 0-for-3 in what would prove to be his last game with the Padres, at Miller Park against the Brewers. The Padres traveled to Arizona after that game, and Rivera was sent to the Minors.

Rivera said, "I didn't know then" that it would be his last Major League stint in three years. "It's pretty weird," he said.

Rivera was hitless in his first three at-bats Friday before hitting a solo home run in the ninth inning of Milwaukee's 7-2 loss to the Cubs. It was his first Major League homer since May 8, 2003.

"I was pretty nervous those first few innings," Rivera said. "Especially those first two at-bats. But after that, I started to calm down a little bit and I made a pretty good swing that last at-bat."

Slumping: Hall entered Saturday's game with 20 strikeouts in his last 49 at-bats.

"He's a little bit like Prince [Fielder], struggling a little bit," Yost said. "He's going through a bit of a strikeout streak. He'll have a good night and then not a good night. [Friday] it was three punchouts and a double play. But he's a guy that can put some offense on the board for us."

Fielder entered the game with just four hits in his last 41 at-bats.

Rainy rehab: Brewers right-hander Tomo Ohka was scheduled to make his second Minor League rehabilitation start on Saturday for Class A Brevard County, but the game was rained out. Ohka (shoulder) and the Manatees will try again on Sunday.

On deck: Left-hander Doug Davis, who has put together quality starts in five of his last six outings, will take the mound against Cubs right-hander Mark Prior in the final game before the All-Star break Sunday. Davis has a 2.74 ERA in 10 career starts against the Cubs, and worked a season-high 8 2/3 innings in his last start against the Reds.