The adversity facing the Toronto Maple Leafs this month will be ratcheted up a notch if No. 1 defenceman Morgan Rielly is unable to play.

Rielly suffered an upper-body injury when he fell awkwardly on his right arm during the second period of Thursday’s 3-2 loss in Philadelphia. Rielly returned to that game but saw limited ice time.

The defenceman sat out Friday’s practice. He returned to the ice during Saturday’s optional morning skate but left earlier than the rest of his teammates.

Rielly will be re-evaluated, according to coach Mike Babcock, but his availability for Saturday’s game against the Ottawa Senators is in doubt.

"He’s been our backbone. He leads the charge on the back end, night in and night out, so we’re hoping he can go," said teammate Connor Brown.

Right wing Brown, who has scored breakaway goals in consecutive outings, is slated for a promotion to the third line, while Mitch Marner moves down to Brown’s spot on the fourth line.