Ben Simmons' abrupt departure against the Milwaukee Bucks on Sunday, will be further evaluated, with concerns on the potential nature of his injury.

The Philadelphia point guard had missed the Sixers' earlier game against the Brooklyn Nets with lower back soreness. He reportedly had discomfort at practice on Thursday, and received treatment, which still resulted in the team holding him out.

Simmons exited Sunday's game after playing less than five minutes, recording five points, two rebounds and an assist - the 76ers ended with a 98-119 loss to the Milwaukee Bucks.

According to ESPN's Adrian Wojnarowski, Simmons was described as being "emotional" when he left the X-ray room in Milwaukee's Fiserv Forum. An MRI will be performed on his lower back on Monday (Sunday US time).

Through his NBA career so far, Simmons had exhibited excellent durability, playing 81 regular season games in his rookie season. He played 79 in his second year, and missed games in 2018, similarly due to lower back tightness.

This season, the Australian All-Star has had a stellar defensive showing, making a strong case for All-Defensive honours, and has helped lead the Sixers during fellow All-Star, Joel Embiid's absence. An extended absence from Simmons would redirect leadership back to Embiid, who had finally removed his finger brace and returned to full play, after missing time from a torn finger ligament. The Sixers' guard rotation would be greatly impacted --especially on defence-- if Simmons experiences downtime, with team likely diverting those minutes to Josh Richardson and Raul Neto at the point guard spot.

The Philadelphia 76ers are currently fifth in the Eastern Conference, sitting 35-22, and play the Atlanta Hawks next, on 25 February, Tuesday at 11 a.m. AEDT.