That all changed Monday, when Mills was in Seattle interviewing for the Mariners' managerial vacancy.
"I think this is his first Major League managing interview, which I don't understand why it took so long," Francona said by phone. "But I know he's prepared. I was talking to him this morning. I know he's excited about it. That's good. I think this means a lot to him."
Mills, who was scheduled to meet with Mariners general manager Jack Zduriencik, is hardly the only Red Sox coach in the mix for the Seattle job.
Third-base coach DeMarlo Hale will be one of seven candidates -- including Mills -- to be interviewed this week, according to a press release issued by the Mariners.
Red Sox pitching coach John Farrell was expected to speak with the Mariners about the vacancy, but he pulled his name out on Monday night.
"I have withdrawn my name for consideration by the Seattle Mariners as they search for a new manager," Farrell said in a statement. "I wish them well as they move forward. My decision is based on family reasons and being committed to the Red Sox Organization. The working relationship shared with Theo and Tito and the resources provided by John Henry, Tom Werner, and Larry Lucchino create a situation that is both challenging and rewarding."
The dynamic of staff members drawing interest for the same job was both exciting and odd for Francona.
"It's exciting," Francona said. "It's weird though, because DeMarlo is also interviewing and so is John Farrell. I've been with Millsy for so long, but I'm so close to all three of them. It's a weird dynamic."
Francona and Mills have been close friends for three decades, going back to when they were teammates and roommates at the University of Arizona. Mills was on Francona's staff for his four years in Philadelphia (1997-2000) and has been the bench coach for the Red Sox since Francona was hired in 2004.
"I think [Mills is] ready for whatever comes his way, but I guess I feel the same way about DeMarlo and John," Francona said. "You certainly want to keep your staff intact, because you like them so much, but you want what's best for everybody. These things have a way of working themselves out. Either way, I'm going to be thrilled for these guys."
As for the Seattle situation, John McLaren was relieved of his duties as Mariners manager in June. Jim Riggleman served as the Mariners' interim manager for the remainder of 2008 and was recently hired to be the bench coach for the Washington Nationals. The Mariners finished 61-101, the worst record in the American League in 2008.
Mills, Hale and Farrell are all greatly respected around the Red Sox for their work ethic and leadership.
To have three coaches drawing interest for the same job is a pleasant reminder for Francona.
"It means that we have good coaches," Francona said. "I think these guys do a great job. But when something like this happens and three of these guys get interviewed, it just kind of reminds you that we are blessed to have such good coaches.
As for Francona, he will take on the role of supportive bystander.
"I talked to all three of them and wished them well and we'll see what happens," Francona said.
Ian Browne is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.