The Philadelphia 76ers are already without point guard Ben Simmons as he undergoes further testing on his back, and now another key player faces an injury concern. Swingman Tobias Harris reportedly suffered a right knee contusion during Saturday night's game against the Milwaukee Bucks, and he is doubtful for Monday's game against the Atlanta Hawks:

This is particularly concerning news, especially considering Harris has played in all 57 games this year.

The 27-year-old has been a steady two-way player for the Sixers, averaging 18.9 points, 6.8 rebounds and 3.0 assists while shooting over 40 percent from the field and close to 36 percent from beyond the arc.

More importantly, Harris has often guarded the opponents' best player, and he has racked up 2.5 defensive win shares thus far, according to Basketball Reference.

The Sixers will most certainly be glad they added both Alec Burks and Glenn Robinson III at the deadline. Each of them figure to see a significant increase in minutes, especially if Harris has to miss an extended period of time.

Regardless, this is poor timing for a Philly team desperately trying to move up in the Eastern Conference standings. The Sixers are currently fifth in the East, and they are just a 1 1/2 games out of the fourth spot. But they are also just 1 1/2 games up on the Indiana Pacers, who are currently in sixth.

To make matters worse, Simmons' injury might be more serious than initially thought. He will undergo further testing on his back on Monday, but the mere aggravation of the injury after the All-Star break is what makes the nature of it more concerning.

If Simmons hits the shelf, the Sixers will be hoping Harris can return in short order.