WACO, Texas (AP) -- Playoff hopeful Baylor is facing a potentially huge loss after staying undefeated, with quarterback Seth Russell set to see a specialist for a fractured bone in his neck.

The extent of Russell's injury won't be known until after that visit early this week, but the second-ranked Bears (7-0) will almost certainly be without the top-rated FBS passer for at least some time when headed into their toughest stretch of the season.

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"Always concerned, 100 percent. First and foremost, about his health and then football," coach Art Briles said after Russell got hurt in the Bears' 45-27 victory over Iowa State on Saturday.

Briles later told ESPN's Brett McMurphy that Russell "would probably be out awhile."

Baylor officials said again Sunday that the timetable for Russell's return was still unknown until after seeing the specialist.

Russell, a devout Christian, posted a message on his Twitter and Instagram accounts that read, "His plan isn't always clear..but trusting in His plan for me. Thanks for all the prayers Baylor."

The message by Russell made no other reference to his injury, or the extent of it.

Immediately after Baylor won its FBS-best 20th consecutive home game, Russell was described as having a strained neck. X-rays and a CT scan later revealed the fractured bone.

Highly-touted freshman Jarrett Stidham would take over for Russell as starter. Stidham has played in every game this season, completing 24 of 28 passes for 331 yards with six touchdowns and no interceptions.

Russell is 119 of 200 for 2,104 yards with FBS-high 29 touchdowns and six interceptions. The junior's 29 passing TDs and six rushing scores match what Bryce Petty had in his 12 games last season for Baylor before being drafted by the New York Jets.

Petty missed only one game last year after cracking two small bones in his back. That was the only game before this season that Russell had started.

Baylor has already moved sophomore Chris Johnson from receiver back to quarterback on the depth chart behind Stidham. Johnson completed his only four passes for 45 yards last season, and has three catches for 37 yards this year.

With an open date before playing Nov. 5, a Thursday night at struggling Kansas State (3-4), there is some extra time for Stidham to prepare as the No. 1 quarterback.

Baylor's next home game is Nov. 14 against 14th-ranked Oklahoma (6-1), before consecutive road games at 12th-ranked Oklahoma State and fifth-ranked TCU, the Big 12's other undefeated teams so far.

Russell's final play against Iowa State was a 4-yard run on third-and-5 with 5:36 left, though it was not immediately apparent he was hurt. There was helmet-to-helmet contact when he put his head down pushing forward, and was tackled in a pile with five Cyclones.

When the Bears called timeout and decided to kick a field goal rather than trying to convert a fourth-and-1, Briles said they "didn't feel like (Russell) was ready to go on that fourth down."

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