Morrow is set to be evaluated in a week but the typical recovery time is four to six weeks, the Thunder said Friday.
The Thunder have been bit hard by the injury bug during training camp, losing both Kevin Durant and rookie forward Mitch McGary for at least the first month to foot injuries. The Thunder expect to have guard Reggie Jackson (wrist) and center Kendrick Perkins (quad strain) available for Wednesday's opener against the Portland Trail Blazers.
With Durant out, Morrow was a strong candidate to slot into the Thunder's starting five at shooting guard. Along with Russell Westbrook, Andre Roberson, Serge Ibaka and Steven Adams, Morrow started the final three preseason games. Now, coach Scott Brooks will be forced to reconsider his starting group again, likely turning to either Jackson, Perry Jones or Jeremy Lamb to fill the role.
Morrow, 29, signed a three-year, $10 million deal with the Thunder over the summer, adding a perimeter sharpshooting element to the team. Last season, Morrow hit 45.1 percent from 3 for the Pelicans. In six preseason games for the Thunder, he knocked down 13 of 29 shots from 3 (44.8 percent).