In Gallagher's last Cactus League outing on Wednesday against Oakland, he walked three of the four batters he faced. He's pitched in four games, and given up five hits and five walks over 6 1/3 innings.
"I wasn't myself yesterday," Gallagher said on Thursday. "It was more like I was passive -- not aggressive. I would rather have had a day like that a couple weeks ago than yesterday."
Gallagher's name has been mentioned in trade rumors, but the right-hander says he's not thinking about that.
"It's never on my mind," he said. "I'm just trying to make an impression."
Ascanio, whom the Cubs acquired from the Braves in December, has given up six runs on 10 hits and four walks over nine innings in nine games this spring.
The spring roster now has 38 players, and includes 19 pitchers, three catchers, 10 infielders and six outfielders.
Carrie Muskat is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.