At the NFL owners meetings, Harbaugh said he hasn't talked to McClain about a potential return. The Ravens hold the rights on McClain, who abruptly retired last offseason.
Two weeks ago, McClain was noncommittal on whether he plans to play this season.
"To me, it all depends on a couple things. Who [is he] as a person right now? Has he grown up?" Harbaugh said. "He had a lot of growing up to do obviously. And how hard he's working, how hard he's working at Alabama right now. If he's working his rear end off, then I'm kind of excited about him. If he's not, then I've got no interest in him being on our team."
The Ravens don't have a pressing need at inside linebacker. The team re-signed Daryl Smith and hopes Arthur Brown steps into a starting role in his second season. The Ravens' backups are Josh Bynes and Albert McClellan, both of whom have starting experience and are core special-teams players.
McClain, the No. 8 overall pick in the 2010 draft by the Oakland Raiders, announced his retirement 10 months ago, stating he wanted "to focus on getting my personal life together."
He re-enrolled at Alabama and told reporters that he needs two summer classes to complete his degree.
The Raiders released McClain last April 5 after a series of off-field issues, including a shooting incident in December 2011 that led to McClain being charged with four misdemeanors. The charges were later dropped after he and the victim reached a financial settlement.
McClain signed with the Ravens five days after being released by Oakland but retired before attending even one practice. The Ravens still retain the rights for the 24-year-old former Alabama standout. In 41 games over three seasons with the Raiders, McClain had 246 tackles and 6.5 sacks.
Harbaugh didn't specify whether there is a time frame in which the Ravens need to know McClain's decision.
"If he unretires or whatever the situation is, then we'll decide whether he is going to be good for our team," Harbaugh said. "And if we think yes, then we have the rights to him and he'll have to come back with us. But if we don't think he'll be good for our team, we'll let him go and play for somebody else. It's all up to Rolando McClain. Who are you? How hard are you working? And how much do you want to play football? Up to this point, he hasn't really wanted to play football. That's what I'm interested in as a coach."