Connor spoke to Orioles manager Buck Showalter on Monday around noon, informing him that he was leaving the team.
"Obviously, it's not something that he just pulled out of the air. He's been thinking about it," Showalter said.
The 61-year-old Connor was well-liked in the Orioles clubhouse and by the organization.
"I don't think people realize the intensity and the toll that these jobs take on guys. Especially guys that care like he does," Showalter said. "He just didn't feel like he was able to provide what was needed. And no one understands what's needed more than Mark Connor."
In his first season as Baltimore pitching coach -- and his 36th season in professional baseball -- Connor oversaw a staff that owns a 4.22 ERA, ranking 11th in the American League. The Orioles have allowed the third-most home runs in the AL, and the club sits in last place in the AL East.
Baltimore was in Toronto on Tuesday to face the Blue Jays, for whom Connor served as a pitching coach for a year and a half in 2001-02. Connor resigned from the Blue Jays on June 5, 2002, out of solidarity to Toronto manager Buck Martinez, who was dismissed the same day.
Adair also joined the Orioles staff this season, after spending the last two as pitching coach with the Mariners. Under his watch, the Seattle team ERA dropped from 4.73 in 2008 to a league-best 3.87 in '09.
Showalter said one of the main reasons Adair joined the team in the offseason was because Connor had agreed to be the team's pitching coach, and reached out to Adair to join the coaching staff. Adair would have been one of the prime candidates to be the team's pitching coach had Connor not taken the job.
"We're fortunate to have Rick here. He's a guy that basically had some other opportunities and came here because of Mark," Showalter said. "In that capacity, we're very fortunate to have a guy here who can hopefully make a seamless transition."
Connor and Adair share very similar pitching philosophies, which Showalter hopes will aid in the transition from one pitching coach to another for his staff. Showalter and Adair sat down with the pitching staff and both catchers to go over the transition, and what the team could expect in the coming weeks.
"Everybody is different on the coaching staff, but Mark and [Adair] share a lot of things," Showalter said. "They share a lot of the same beliefs -- that's why they get along so well and have the track record they do everywhere they've been."
Adair has spent more than seven full seasons as a big league pitching coach -- two with the Mariners (2009-10), two with Cleveland (1992-93), and three with Detroit (1996-99). Before his stop in Seattle, he was the Rangers' Minor League pitching coordinator for four years, a position he also held with the Braves from 2000-03.
Taking Adair's place as the interim bullpen coach is organizational hitting instructor and evaluator Terry Crowley. Crowley will be a stopgap for at least the Toronto series, and possibly longer as the team searches for a new coach.
"We didn't want to knee jerk," Showalter said of hiring a new coach. "We're very fortunate to have somebody with [Crowley's] experience."
Arden Zwelling is an associate reporter for MLB.com.