The Philadelphia 76ers will get a key reinforcement on Monday night as they take on the Oklahoma City Thunder. Point guard Ben Simmons, who has missed the last four matchups for the Sixers, will be back in action after dealing with a non-COVID illness.

Simmons' absence from the Sixers started last Monday as they were gearing up to take on the Golden State Warriors. On the day of the matchup, the veteran guard showed up on the injury report listed as questionable due to an illness.

Eventually, the Sixers ruled him out. Going into last Wednesday's game against the Phoenix Suns, Simmons was in the same position. After being questionable for most of the day, the 76ers ruled Simmons out before the matchup. 

The following night, the Sixers faced off against the Milwaukee Bucks for the second time this season. Simmons, who was questionable to even make the trip, was ruled out as it was reported he didn't travel with the team.

By Friday night, the Sixers didn't hesitate to rule Simmons out for Saturday's matchup as he missed his fourth-straight game. Beforehand, Doc Rivers confirmed that Simmons was dealing with the flu and mentioned that Simmons was feeling better but not exactly feeling great.

When Sunday rolled around, the 76ers once again ruled Simmons out early. However, they changed course on Monday as the team upgraded Simmons to questionable when they submitted the afternoon injury report. 

After Simmons went through shootaround on Monday, the team expected him to be able to play. Fortunately for the Sixers, Simmons was cleared for action and is available to play against the Thunder on Monday night. 

Justin Grasso covers the Philadelphia 76ers for Sports Illustrated. You can follow him for live updates on Twitter: @JGrasso_ & Instagram: @JGrassoNBA.