PITTSBURGH -- With Carlos Lee making his debut with the Marlins on Thursday, a day after he was traded for a pair of prospects, the Astros had Chris Johnson playing first base for the series finale against the Pirates with Matt Dominguez making his Astros debut at third.

Dominguez, 22, was acquired from the Marlins with left-hander Rob Rasmussen, who is going to Double-A Corpus Christi.

Astros manager Brad Mills indicated Johnson would play first base for the four games until the All-Star break, but wouldn't commit to anything beyond that. He was also asked if Brett Wallace was in the team's plans at first, but was non-committal.

"We've got four games now before the All-Star break and we're going to go this route for these four games and make some adjustments and see where we're at and let guys get at-bats in those positions and then we can go from there," Mills said.

Matt Downs and Scott Moore could also get some time at third. Johnson played a lot of first base in Spring Training and handled the position adequately. He has played only two innings at first base this year.

"I played some games over there this season and got a bunch of starts in Spring Training," he said. "It's a knockdown position. I'm fairly comfortable over there, so it's not something I'm worried about."

New addition Dominguez makes Astros debut at third

PITTSBURGH -- Matt Dominguez, one of two players the Astros acquired from the Marlins in the Carlos Lee trade on Wednesday, arrived at PNC Park and was in the lineup against the Pirates on Thursday, starting at third base.

"It's kind of exciting and nerve-wracking and a feeling I've never had before," Dominguez said of the trade. "It was definitely a new experience, and it's nice to get here and meet some of the guys and go out there and play again."

Dominguez, 22, isn't the youngest player on the team, but he certainly looks the youngest.

"He's 22 and he looks 15, but he's a great kid," Astros manager Brad Mills said. "We're looking forward to seeing him at this level and go from there."

Dominguez has played the entire season at Triple-A New Orleans, where he hit .234 with 14 doubles, seven homers and 46 RBIs in 78 games. The Zephyrs were playing the Astros' Triple-A affiliate in Oklahoma City when the trade went down, and Mills called RedHawks manager Tony DeFrancesco to get a scouting report.

"I had a long talk with Tony today and got his thoughts," he said. "He thinks he's got something special with the bat and, at 22, could come around and be a real good hitter, and that's what our scouts said, too."

Mills sits outfielder Schafer Thursday vs. Bucs

PITTSBURGH -- One day after being removed during the game for throwing to the wrong base and for what manager Brad Mills described as "behavioral reasons," center fielder Jordan Schafer wasn't in the lineup Thursday. Schafer had been starting against right-handed pitchers.

Mills hasn't expounded on what behavioral issues Schafer has had, but Schafer on Wednesday said he respected Mills' decision and wanted to put the issue behind him. Mills planned to have a sit-down meeting with Schafer on Thursday.

"We just want to talk and go through some things and get some things squared away," Mills said. "That's kind of where we're at. I like Jordan. He's got all kinds of ability. We want to try to get that behavior to match that ability, and that's where we're at. This is not him against me or anything else. This is not an issue."

Schafer has made 63 starts in center field and is hitting .236 with three homers, 20 RBIs and tied for sixth in the National League with 19 stolen bases.

Mills, Astros players react to Lee trade

PITTSBURGH -- While the Astros were killing time in the clubhouse before taking batting practice on Thursday, some of the players were watching former teammate Carlos Lee go 2-for-4 in his debut with the Marlins, who traded for him on Wednesday.

Lee was a mainstay with the Astros for 5 1/2 years, and it was strange to see his locker cleared out in PNC Park.

"It's always strange when you see a guy playing in a different uniform, and the next thing you know, he's in another one, especially when he was in ours," third baseman Chris Johnson said. "It's a little different, but that's the nature of the beast."

Astros manager Brad Mills was instructed to pull Lee from the game in the seventh inning Wednesday because of the trade. Mills admitted the trade to the Marlins caught him off-guard, though the Astros tried to send Lee to the Dodgers earlier in the week.

"They came to me in the seventh inning and said, 'Hey, get him out of the lineup, he's been traded,'" Mills said. "The game's over and I go in and talk to Carlos and wished him well and gave him a hug and thanked him and now he's gone. Now we move on down the road."

Worth noting

• After sending starting pitcher Dallas Keuchel to Triple-A Oklahoma City following Wednesday's game, the Astros on Thursday recalled relief pitcher Enerio Del Rosario from Oklahoma City, giving Houston an eight-man bullpen until the break.