It's one of the few things he's done different from the guy he's replacing.
The Cardinals' bench coach became their acting manager when La Russa went home to recover from the shingles. Pettini led the Cardinals to a pair of wins during a three-game series in Chicago, and was in charge for a weekend series in Cincinnati matching the NL Central's top two teams.
"To me, it's a blast," Pettini said Friday, a few hours before the first pitch. "It gets a little nerve-racking at times because I haven't been doing it in a while. The St. Louis Cardinals, the Cincinnati Reds, 1-2 in the division: This is baseball. This is competing. It's what it's all about, really."
The 56-year-old coach managed for eight seasons in the farm system, most recently at Triple-A Louisville in 1995. He's been the bench coach for the past 10 seasons, giving him a chance to learn how La Russa handles a lineup and pitching staff.
Mostly, he's trying to copy him until he gets back.
"I've been around him so much," Pettini said. "I think a lot of it has rubbed off. I used to be more aggressive, especially baserunning-wise. With the offense we have, you watch Tony. Sometimes I'm thinking we can steal third here or maybe we can steal second. He understands we've got (Albert) Pujols, (Lance) Berkman, (Matt) Holliday coming up. You really don't need to push it.
"Yeah, a lot if it's rubbed off."
The toughest part for Pettini has been getting comfortable being in charge of everything. He talks to La Russa on the phone each day to check up and trade thoughts.
"Probably the toughest thing for me at first was to be able to stay up on everything and have it come easily," he said. "It takes time, doing it for a while.
"It's getting a little easier. It's not going to come out right away, but I'm doing the best I can."
He gets to match in-game decisions with Dusty Baker this weekend. They shook hands at home plate after taking out their lineup cards.
"He doesn't have a long enough track record to have any tendencies," Baker said. "There's a good chance he knows what I'm going to do better than I know what he's going to do. He's been over there watching me for years."
Baker and the Reds overtook the Cardinals last season, winning the NL Central title. Cincinnati beat up on the rest of the division but had trouble with St. Louis, which won 12 of their 18 games and four of their five series. The Cardinals took two of three in St. Louis last month.
St. Louis arrived in town leading Cincinnati by 1½ games. Baker dismissed a suggestion that the Reds need to gain confidence by beating the Cardinals.
"I don't think in those terms," he said. "I mean, it's important that we finish ahead of the Cardinals, regardless of who beats who. That's what's important. I know everybody makes a big deal out of it.
"You've got to forget what happened last year. Let's ask this question if the same thing persists three months from now. You've got to get out of the past, you've got to get out of history and get to the now."
There's a little history still simmering between the teams.
Reds second baseman Brandon Phillips sparked a brawl last season by calling the Cardinals "whiners," using demeaning language that riled St. Louis. Right-hander Johnny Cueto was suspended for seven games for kicking catcher Jason LaRue and pitcher Chris Carpenter during the scrum.
Phillips was diplomatic on Friday, saying it's just another series. He also played down the suggestion that the Reds need to beat the Cardinals.
"They kicked our butts last year, and we still made the playoffs," Phillips said. "Don't get me wrong — beating them would be great, a beautiful thing. But making the playoffs is much better."
Cueto is scheduled to start on Saturday, the first time he'll face the Cardinals since the game involving the brawl.
"I don't think our guys have anything more than going out there and trying to beat him," Pettini said. "What happened last year, I think, still leaves a mark a little bit. They remember it and think about it, but we've got to go out and play the series just like we did in Chicago."