The Tigers often use utility man Andrew Romine as a defensive replacement. Castellanos is in his third full season as a third baseman, and though fielding metrics indicate he is still a below-average defender, his numbers have improved since last season. Castellanos admits he is still learning, but he's becoming more comfortable at third.
"Everybody in this clubhouse knows I want to be in the game," Castellanos said, "but it's [Ausmus'] decision to put the guys on the field. ... If it's not me, then my job is just to play better to make that decision harder and harder."
Slowly but surely, Castellanos is doing that. He made a series of good plays in Monday's 10-9 extra-inning win against the White Sox, including a diving stop to rob Tim Anderson of a hit in the third inning.
With Victor Martinez limited to pinch-hitting and unable to run the bases, Castellanos stayed in at third all night so Ausmus could have more options off the bench. Castellanos entered Tuesday's game hitting .304 with 12 home runs, so as his defense improves, his bat gives him an advantage in gaining Ausmus' trust in the field.
"I think as long as you think there's a significant difference in defensive ability between two players at any position, in a game late, you probably make a move with the better defensive player," Ausmus said. "If Nick continues to get better and that gap shrinks significantly, now maybe it's not worth making that move anymore."
• Martinez was out of the lineup for the second consecutive day Tuesday as he deals with soreness in his right knee. Ausmus said the Tigers will continue to treat him as day-to-day.
• Center fielder Cameron Maybin was also out of Tuesday's lineup as Ausmus looks to be careful with Maybin, who is dealing with nagging pain in his left wrist. Romine started in Maybin's place.
"It's two-fold," Ausmus said. "I got to get Romine in there once in a while, and we have to find spots to get Maybin out of there so [the wrist] doesn't act up. Try to avoid having to go through the three days off, having to get a shot type-things."
• Ausmus is also looking to find a day off for Miguel Cabrera, but Martinez's injury makes it difficult. Ausmus said Cabrera hasn't complained of fatigue, but he is hitting only a combined .163 in the eighth and ninth innings this season.
"Probably some time on this road trip I'll have to bite the bullet and give him an off day," Ausmus said.
Cody Stavenhagen is a reporter for MLB.com based in Chicago.