Despite the injury, Brees hopes to continue playing in the Saints' final two games of the regular season, the source said, but the injury complicates his ability to throw because he throws off that right foot.
Manning has missed the past five games with his partially torn plantar fascia. Former Saints tight end Jimmy Graham never missed a game in 2013 when he had a partially torn plantar fascia. But Graham had the luxury of a bye week to recover, and his snaps were significantly limited when he did return.
Anderson has not yet made a recommendation to Brees, who is believed to be considering several treatment protocols, the source said.
Coach Sean Payton said Wednesday, "We're kind of taking it day by day. I know he's had it looked at, he's had an MRI. I think each day we'll gather more information and have a better idea of where he's gonna be as it pertains to playing in this game or not."
The team is not scheduled to practice for the first time this week until Thursday.
Brees was hurt during the second quarter of Monday night's 35-27 loss to the Detroit Lions. He appeared to step awkwardly on the foot while escaping pressure from defensive end Ezekiel Ansah on a third-down incompletion. He landed awkwardly and appeared to come up limping.
Brees was taped up on the sideline and returned to play some of his best football -- throwing three second-half touchdown passes during a futile comeback attempt.
Still, he was noticeably hobbled by the injury.
The Saints have a short week of preparation before their next game. Brees plans to treat the injury aggressively and hopes to play on Sunday at home against the Jaguars, the source said, but he is expected to be listed as day-to-day.
Flynn signed with the Saints last month after Saints backup Luke McCown had season-ending back surgery, and Flynn has been serving as Brees' primary backup. But with the Saints at 5-9 and out of the playoff race, they could be tempted to give some experience to Grayson, a third-round pick out of Colorado State.
Brees, 36, had never missed a game for injury in his 16-year NFL career before this season. But he missed one game with a shoulder injury in Week 3 at Carolina.
Brees has thrown for 4,135 yards with 28 touchdowns and 11 interceptions this season. He just became the fourth quarterback in NFL history to throw for 60,000 career yards on Monday night. And last week he passed Dan Marino for fourth place all-time in touchdown passes (now 424).
Brees has one year remaining on his contract with the Saints through 2016. He is scheduled to make $20 million in salary and bonuses, but he will cost $30 million against New Orleans' salary cap -- the highest figure for any one player since at least 2002, according to ESPN Stats & Information.
The Saints will have to decide whether they want to extend Brees' contract to help provide cap relief this offseason; they are already over the NFL's projected cap of $150 million with just 41 players under contract.