CINCINNATI -- Reds manager Dusty Baker learned about Nationals rookie Bryce Harper's self-inflicted head injury from his 13-year-old son Darren. Harper, who was 0-for-5 Friday, was bloodied and needed 10 stitches after swinging his bat against a wall in the Washington dugout area. The bat bounced back and hit him above his left eye.

"Sometimes that's good for kids like my son's age to see how not to do things," Baker said. "You can tell them about the repercussions on how not to act, but it's different for them to see it."

In his younger playing years with the Braves, Baker was admittedly prone to outbursts of his own. That was until teammate Hank Aaron stopped him with a hand on his shoulders.

"One time I threw my helmet down in front of Hank Aaron," Baker explained. "He told me, 'I don't want to see you throw that helmet down again.' He said, 'It ain't the helmet's fault. Put that helmet back where it came from, go over there and sit down, and figure out how you are going to get them next time.'"

Rolen lands on DL with ailing shoulder

CINCINNATI -- Reds third baseman Scott Rolen was already pained by his lack of production this season. And now he is dealing with the return of pain in a familiar place.

On Saturday, Rolen was placed on the 15-day disabled list with a strained left shoulder. The club purchased the contract of third baseman Mike Costanzo from Triple-A Louisville to join the 25-man roster.

"We're going to address it and take some time off," Rolen said after the transaction was made. "[I will] try to do a lot of stretching, try to get a lot more mobility, and try to get the inflammation out of there that is causing the problems."

Rolen was examined on Saturday evening by team medical director Dr. Tim Kremchek. This is the same shoulder that needed surgery multiple times over the years, including last season, when the 37-year-old missed most of the second half.

"If we want to talk about the pink elephant in the room, I've been struggling with it," Rolen told MLB.com before his appointment.

Rolen called head trainer Paul Lessard earlier on Saturday to let him know his shoulder was hurting, and then spoke with manager Dusty Baker after reaching the ballpark. Baker started Todd Frazier in Rolen's place at third base.

"It's not a surgical procedure, where we're going down that road again," Rolen said. "I've had a tough time with it, and I'm in a bad spot right now with it. It's inflammed, fatigued, and it needs to settle down and be rested. I'm not sure if there will be injections or what we'll do with cortisone to try to calm the thing down, but we're going to treat it as well as we can."

In 29 games this season, Rolen is batting .174 with two home runs, 11 RBIs and a .238 on-base percentage. During Spring Training, Rolen looked healthy and played well, as he batted .356, but he has not been able to carry that performance into the regular season.

"It's a tough question, because it's an easy excuse," Rolen said of his shoulder. "I'm responsible for my at-bats when I go out on the field. I have not contributed. I have not been productive in any capacity."

Rolen is in the final year of a contract that is paying him $6.5 million this season.

"I'm not helping anybody right now," Rolen said. "I'm not helping the ballclub right now. I'm probably hurting the ballclub right now, with the way I've been swinging the bat and have been playing."

In a combined 34 games with Louisville and Double-A Pensacola, Costanzo batted .303 with six homers and 24 RBIs. When he appears for the Reds, it will be his big league debut. The 28-year-old was a second-round Draft pick of the Phillies in 2005, and joined Reds in 2010 after playing independent ball for Camden in the Atlantic League.

Leake slated to take next turn in rotation

CINCINNATI -- All signs appear to point to pitcher Mike Leake getting another start for the Reds. Leake is still scheduled to face the Mets on Wednesday at Citi Field.

Leake, who is 0-5 with a 7.11 ERA in six starts this season, lasted a career-low three innings and allowed six runs in Friday's 8-3 loss to the Nationals.

"We haven't covered it yet. I would like to think so," Reds manager Dusty Baker said about Leake starting Wednesday. "You don't want somebody looking over their shoulder like they're on death row or something, either. We are going to a bigger ballpark in New York, which will probably help, too."

In Leake's 31 2/3 innings, he has allowed 40 hits and 11 walks with 16 strikeouts. He's allowed five or more runs in four of his six outings.

"There's such a thing as bad starts sometimes," Baker said. "We know he can pitch, but hopefully we can get it straightened out. We're confident he can still pitch. So the answer right now is yes."

Frazier making most of opportunity this season

CINCINNATI -- Reds rookie infielder/outfielder Todd Frazier certainly hasn't squandered his opportunity. Frazier, who started in place of the struggling Scott Rolen at third base on Saturday, took a .364 average into the game vs. the Nationals.

Frazier was initially recalled from Triple-A Louisville on April 17 when Miguel Cairo went on the disabled list. When Cairo was activated, the club outrighted Willie Harris in order to keep Frazier.

"It's up to the player. I give guys opportunities, and hopefully he can continue swinging well," Reds manager Dusty Baker said. "He's done better here than in Triple-A."

Frazier ranks second in the Majors with five hits as a pinch-hitter. Saturday marked his fifth start at third base, and he also started on Wednesday in left field.

"The opportunity presented itself to him, especially when some of the other guys struggled," Baker said. "We are right-handed dominant, which we would like to do something about in some point in time, especially off the bench."

Worth noting

• Saturday was Joey Votto Gold Glove bobblehead night for the first 25,000 fans that entered Great American Ball Park. The Reds announced the game as a sellout, the third of the season.