Drew Brees has been diagnosed with multiple rib fractures and a collapsed right lung, a person with knowledge of the situation said Monday.

The person spoke on condition of anonymity because the Saints have not announced specifics about Brees' injury, which the 41-year-old quarterback said occurred on a heavy hit by San Francisco defensive lineman Kentavius Street in the second quarter of New Orleans 27-13 victory over the Niners on Sunday.

CLICK HERE FOR MORE SPORTS COVERAGE ON FOXNEWS.COM

Brees' injuries, which were first reported by ESPN, are expected to sideline the quarterback for multiple weeks. Two of the Saints' next three games are against the Falcons, first on Sunday in the Superdome and then in Atlanta on Dec. 6. In between, New Orleans visits Denver on Nov. 29.

Saints coach Sean Payton said Monday he would not comment on any injuries before the first required injury report of this week on Wednesday.

But with Brees virtually certain to miss upcoming games, the Saints' offense is likely to be run primarily by Jameis Winston, a 2015 first overall draft choice by Tampa Bay whom New Orleans signed to a one-year contract as a free agent this offseason. Taysom Hill, a utility player who intermittently takes over for Brees on option plays — but also plays tight end and on special teams — also could see his snaps at quarterback increase, depending on Winston's performance.

While Brees initially missed just two plays after the hit by Street and returned for another touchdown drive in the final two minutes of the half, he told Payton he did not feel fit to continue in the second half on Sunday. Winston took most of the snaps after that, with Hill also running a number of plays behind center.

Winston completed 6 of 10 passes for 63 yards and Payton said he thought Winston “did a good job,” but added that the offense as a whole was hampered by injuries to other key regulars, including receiver Tre'Quan Smith and tight end Josh Hill, who both left with concussion symptoms.

Winston was a starter for most of five seasons in Tampa Bay, but became a free agent after former Patriots QB Tom Brady agreed to join the Buccaneers.

“Both (Winston) and Taysom have a good feel of what we're trying to do," Payton said. "They pick things up and I feel like it's a good (quarterback) room.”

CLICK HERE TO GET THE FOX NEWS APP

The Saints have not been critical of the nature of Street's hit, which came on what would have been a sack had it not been flagged for a personal foul. Street got a clean shot on Brees, de-cleated the quarterback and came down hard on the right side of Brees' torso.

When asked about the play Monday, Payton said the only hit that he viewed as deserving of a personal foul was when San Francisco safety Jimmie Ward hit Smith with a shoulder pad to the helmet, apparently knocking Smith unconscious as the receiver tried to catch a pass over the middle. No flag was thrown on that play.

“In my humble opinion, saw really one flagrant hit worthy of personal foul and that was the hit on Tre'Quan,” Payton said.