Denver Nuggets forward Michael Porter Jr. is out for the "foreseeable future" as he continues to undergo testing on his back, according to coach Michael Malone.

Porter exited Saturday's win over the Houston Rockets in the first quarter with what the team called back tightness. He was ruled out for Monday's game against the Miami Heat with lower back pain.

Malone said before Monday's game that the team is being cautious with their young star, noting that Porter "could be back in a week. It could be more than that. I don't know."

Porter, 23, was one of the top prep prospects in the country before undergoing a back surgery that derailed his freshman season at Missouri. He underwent another procedure after the Nuggets drafted him in 2018 and went on to miss his entire rookie season.

He bounced back the following year and is coming off a season where he averaged 19 points while shooting 54.2% from the field and 44.5% from 3-point range.

Porter signed a 5-year, $173 million extension this past offseason, but had been struggling to start the season.