Boyer is expected to be at Busch Stadium and available to pitch for Tuesday's 7:15 p.m. CT game against the Mets. The Cardinals will demote a position player to make room for him. That will likely be David Freese, though general manager John Mozeliak did not announce the corresponding move in a conference call on Monday afternoon.

Boyer, 27, got off to a rough start with Atlanta in 2009 and was designated for assignment. In three appearances, he allowed six runs in 1 1/3 innings. That follows a major second-half fade in '08 after an excellent beginning to the season.

If Boyer can repeat his first-half 2008 performance -- a 3.93 ERA, 45 strikeouts and 18 walks in 52 2/3 innings -- he'll be a significant asset to the Cardinals' bullpen. Of course, that's far from a guarantee.

"We do think this is a fresh start for him and one that will give him an opportunity to show what he's capable of doing," Mozeliak said.