The GM, talking as the Cardinals wind down spring training in Jupiter, Fla., said the team will likely place Motte on the disabled list with the flexor muscle strain to start the season as it further explores immediate options for the right-hander, the St. Louis Post-Dispatch reported.
The Cardinals said Saturday that Motte had stopped throwing following the results of an MRI a day earlier.
Motte pitched an inning against the New York Mets on Thursday in Port St. Lucie, then told the team his forearm tightened up on the bus ride back to the Cardinals' spring training complex.
"Right now it's going to slow him down," Mozeliak said. "We're certainly going to be aggressive with the rehab."
In January, Motte, 30, agreed to a $12 million, two-year contract extension to avoid salary arbitration after posting a career-high and NL-best tying 42 saves in 49 chances in 2012, when he was 4-5 with a 2.75 ERA. Motte is 17-13 with a 2.87 ERA and 54 saves since his major league debut in 2008.
Motte was 0-0 with one save and a 5.00 ERA in nine innings during spring training.
Mitchell Boggs will get the first shot to serve as the Cardinals' closer while Motte recovers.
Information from The Associated Press was used in this report.