Birmingham City 1 Newcastle United 1: Mitrovic blow as Benitez's side held in FA Cup
Aleksandar Mitrovic was stretchered off as Newcastle United were held in the FA Cup by Birmingham City.
The striker suffered what looked like a knee injury as Daryl Murphy gave Rafa Benitez's side an early lead at St Andrew's.
But Lukas Jutkiewicz's 42nd-minute strike earned the home side a replay.
The result means Newcastle's Championship fixture against Brentford at Griffin Park will now be played on Saturday, January 14.
United manager Benitez had made eight changes for the third-round tie.
Massadio Haidara made his first appearance since October 2015, while Murphy, Achraf Lazaar, Cheick Tiote, Grant Hanley and Matz Sels were also handed rare starts.
Mitrovic suffered the injury as Murphy scored his first goal for the club.
Birmingham goalkeeper Adam Legzdins caught the striker's leg with his studs as he attempted to block Murphy's close-range shot.
Murphy netted at the second attempt in a crowded goalmouth after Achraf Lazaar swung in a corner.
However, the goal came at a cost.
And Mitrovic was given oxygen by medics as he was taken off the field amid chants of "Mitro, Mitro, Mitro" from the club's 4,671-strong travelling support in the Railway End.
Benitez sent on Yoan Gouffran to replace the striker.
Birmingham recovered from a slow start and started to cause problems as the half-time break neared.
And their pressure told in the 42nd minute when Lukas Jutkiewicz scored with a tap-in after Jonathan Grounds crossed into the box.
Benitez replaced a rusty-looking Cheick Tiote with Isaac Hayden in the 65th minute, and Matt Ritchie came on for Haidara.
Ritchie's introduction saw United revert to a flat back four for the last 20 minutes.
But Newcastle couldn't force a breakthrough, and the two sides will meet again at St James's Park on Wednesday, January 18.
BIRMINGHAM CITY: Legzdins; Spector (Dacres-Cogley, 44), Shotton, Robinson, Grounds, Kieftenbeld, Gleeson, Davis, Fabbrini (Stewart, 79), Adams, Jutkiewicz. Subs not used: Kuszczak, Tesche, Cotterill, Brown, Morrison.
NEWCASTLE UNITED: Sels; Lascelles, Hanley, Haidara (Ritchie, 70); Yedlin, Anita, Tiote (Hayden, 65), Colback, Lazaar; Murphy, Mitrovic (Gouffran, 10). Subs not used: Darlow, Dummett, Clark, Gayle.
Goals: Murphy 5, Jutkiewicz 42
Bookings: Hayden 68
Referee: Neil Swarbrick (Lancashire)
Attendance: 13,171 (4,671 Newcastle)