QB won't play vs. undefeated Vikings
Plummer, who missed last week's game against Pittsburgh with a shoulder injury, initially injured his foot against Kansas City on Oct. 5.
The Broncos medical staff believes Plummer likely suffered a stress reaction in his foot that didn't show up on X-rays, then broke the foot at his home Monday night.
"He fractured his left third metatarsal," Broncos trainer Steve Antonopulos said Wednesday. "We X-rayed it right away in Kansas City, and nothing showed up. We treated it the majority of last week, and he actually ran on Monday.
"Then on Monday night, while getting up from watching television, he felt a pinch, tweak, pop -- whatever you want to call it."
Plummer underwent more treatment Tuesday for what was believed to be a strained ligament.
"He came in this morning very tender and you could feel a click and a pop," Antonopulos said on Wednesday. "There wasn't any question that he needed another X-ray."
That X-ray showed a clean break in the middle of Plummer's left foot.
Asked the timetable for Plummer's recovery, Antonopulos said, "The doctors say about four weeks."
Added Plummer, "At least it's not a season-ending injury."
Veteran Steve Beuerlein, who played in Plummer's absence against Pittsburgh, now will get more extended work.
Beuerlein, 38, completed 17 of 28 passes for 172 yards, with two touchdown passes and two interceptions last week.
Plummer fell on his right shoulder in Week 2, has been receiving regular treatment for the injury, and even managed to start and finish three games while battling the pain. He received a painkiller injection last Sunday, was listed as the No. 2 quarterback, and would have played if Beuerlein had been injured.
"I'm still shocked," Plummer said. "It's weird. I didn't think there was anything wrong with my foot. It was sore after the Kansas City game, but my mind was more on my shoulder."
The Broncos (5-1) play at Minnesota and Baltimore before returning home for a Monday night game against New England the next three weeks, then have a bye.
Minnesota is coming off a bye week and will welcome the return of Culpepper, who missed two games because of a back injury.
Broncos trainer Steve Antonopulos said Plummer's foot was X-rayed in Kansas City and nothing showed up. He said Plummer ran on Monday.
Plummer said he felt "a little pop" when he got up off his couch on Monday night.
"I thought it was just a strain," he said. "It's kind of a freak deal. But if it happened, it happened for a reason. Maybe it's to get my shoulder back healthy so when I do come back in a few weeks, I will have no excuses."
Plummer will wear a boot cast for the next week, then will begin some rehabilitation and conditioning exercises.
Len Pasquarelli, a senior NFL writer for ESPN.com, contributed to this report.
Information from The Associated Press was used in this report.
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