Mason surprised the Ravens on July 13 by abruptly ending his 12-year NFL career. Mason, 35, led Baltimore in catches and yards receiving last year, but said he was "ready to see what else life has to offer."
After speaking with Mason on the phone Tuesday night, Harbaugh maintained hope that Mason would have a change of heart soon after the start of training camp next week.
"I think it's real honorable what he's doing in the sense that it would be easy for a guy to just come in and go through the motions. Derrick does not want to go through the motions," Harbaugh said Wednesday. "He wants to make sure he's in the right frame of mind to compete at the level he's competed at his whole career, which is a warrior-type level.
"He's ready physically. He's in good shape and he's healthy. He just wants to decide if he's mentally ready," Harbaugh said. "It's really open right now. I'm optimistic and hopeful that he'll be there, but if he's not there, we'll be support and respect his decision either way."
Harbaugh said his conversation with Mason covered "family, his contract, the team, his feeling about competing and playing, what it's like to have a long career." The two also discussed the death of Steve McNair, Mason's close friend and former teammate.
"He was really open and up front," Harbaugh said of Mason. "It was two guys just trying to see what's down the road."
Upon announcing his retirement, Mason said he would decline interviews over the next two weeks.
Mason caught 80 passes for 1,037 yards and five touchdowns last season. He also had 12 catches for 190 yards and a touchdown in three playoff games. Without him, Baltimore's most accomplished wide receivers are Mark Clayton and Demetrius Williams.
"From a coaching standpoint, I think we have a chance to be a really good team, and if Derrick Mason is a part of it, that makes us even stronger," Harbaugh said. "But if he's not, we're still going to be a really good team. It comes down to Derrick and where his mind is at. He's the only one that can decide that."
The Ravens will hold a tryout for several second-tier receivers Friday, but probably won't make a major move before they're sure Mason won't be back.
"Up until Derrick officially retires, then he's still a member of the Baltimore Ravens," general manager Ozzie Newsome said. "We're OK with what we have, but we're always trying to get better. If there was a player we available in May or June that we thought could help our football team, we would have gotten him at that point."