McCaffery said Thursday at the Big Ten media day that Gatens may miss Iowa's first two games but should be back after that.
Gatens, the team's leading scorer last season with 12.3 points per game, tore the tendon during practice Tuesday and is scheduled for surgery Thursday.
Gatens was an honorable mention All-Big Ten pick in 2009-10, leading the Hawkeyes in free-throw and 3-point shooting percentage and ranking second in steals and assists.
Gatens' injury also opens the door for freshman guard/forward Devyn Marble, the son of Iowa great Roy Marble, to get more opportunities in nonconference play. The Hawkeyes could also lean more heavily on sophomore swingman Eric May, perhaps the most athletic player McCaffery has at his disposal.
Iowa finished 10-22 last season and 4-14 in the Big Ten. The Hawkeyes have been slated for the Big Ten basement yet again -- and losing Gatens for an extended period will certainly lower those expectations further.