Jonas Valančiūnas joins a growing list of injured Nuggets, including four starters. Photo by Ron Jenkins / Getty Images

Add center Jonas Valančiūnas to the long list of Denver Nuggets unavailable due to injuries.

The backup big man, thrust into a starting role after Nikola Jokić hyperextended his left knee Monday night against the Heat, hurt his calf in the third quarter against the Toronto Raptors on Wednesday night. Valančiūnas will be out for at least a month, a team source told The Athletic, with the Nuggets planning to reevaluate him after four weeks.

The Nuggets were already down four starters: Forward Aaron Gordon (hamstring injury on Nov. 21) and guard Christian Braun (left ankle sprain on Nov. 12) may return at the end of Denver’s road trip, which wraps up Jan. 7 in Boston. Forward Cam Johnson (right knee bone bruise on Dec. 23) isn’t scheduled to return to the court until late January at the earliest. Jokić is out at least a month.

Valančiūnas, in his 14th season since the Raptors selected him fifth overall in the 2011 draft, scored 17 points and pulled down nine rebounds in 23 minutes Wednesday, his first start of the season. The Nuggets traded for Valančiūnas — who considered an offer to join Greek club Panathinaikos Athens in the offseason — to give them a strong interior presence when Jokić was on the bench.

The Nuggets are 23-10, third place in the Western Conference. Their seven-game road trip continues Friday against the Cleveland Cavaliers, with stops in Brooklyn, Philadelphia and Boston before Denver returns to the Mile High City on Jan. 9 against the Atlanta Hawks.

Sam Amick is a senior NBA writer for The Athletic. He has covered the Association for the better part of two decades while at USA Today, Sports Illustrated, AOL FanHouse and the Sacramento Bee. Follow Sam on Twitter @sam_amick