Assistant general manager Mike Chernoff -- in Toronto for the season-opening set with the Blue Jays -- explained that the move was aimed at protecting the ballclub in the event that Kazmir, who tweaked an abdominal muscle while playing catch during Monday's workout, is unable to make his first scheduled start on Saturday.
"Obviously it's a little bit of a strange move coming on our opener," Chernoff said. "The reason for it is that Scott felt some discomfort. He threw his side session and felt a little discomfort in sort of the rib cage or abdomen region, so he'll be questionable. With some uncertainty about Saturday's start, we wanted to add him to the roster."
By putting Kazmir on the active roster now, they can backdate any possible stint on the disabled list to Tuesday.
Chernoff would not speculate which Triple-A starter might replace Kazmir if the lefty does need a stint on the disabled list. If he's feeling better Wednesday, Kazmir will throw a bullpen session. Following that workout, the Indians will likely have a better idea about Kazmir's status for Saturday's game against the Rays.
Potential replacements could include Daisuke Matsuzaka, Corey Kluber or Trevor Bauer, who are all at Triple-A Columbus.
"The hope is that he'll go out and throw his side [session] tomorrow and pitch Saturday," manager Terry Francona said on Tuesday. "In case that isn't the case, we have contingency plans."
Kazmir, 29, earned the fifth spot of the rotation as a non-roster invitee for the Indians this spring, allowing nine runs (eight earned) on 29 hits with 23 strikeouts and only three walks in 21 innings, which covers four Cactus League appearances and a pair of Minor League outings.
From 2005-08, Kazmir was a standout starter for Tampa Bay, going 45-34 with a 3.51 ERA over 689 2/3 innings and 742 strikeouts, including a league-leading 239 in '07. Kazmir then went 19-24 with a 5.54 ERA in 55 outings between 2009-11. After he went 0-5 with a 17.02 ERA in five starts at Triple-A Salt Lake in '11, he was released by the Angels.
Kazmir pitched for the Sugar Land Skeeters in the independent Atlantic League last season and for Carolina in the Puerto Rican Winter League over the offseason. He inked a Minor League contract with the Tribe during the winter and displayed a fastball in the 90-92-mph range this spring.
Hagadone, 27, posted a 0.93 ERA in 9 2/3 Cactus League innings this spring, helping him initially win a spot in Cleveland's bullpen.