Joe Willock raised a finger to his lips before letting out a trademark smile. A week after experiencing unimaginable racist abuse, the midfielder stepped up to fire Newcastle United into the FA Cup fifth-round.

Willock embodied the fight much-changed Newcastle showed in this 3-2 victory against Birmingham City. Newcastle had to 'stand up and scrap' in the words of Alan Shearer - and the Magpies had the bumps and bruises to prove it.

There were seven yellow cards, 23 fouls combined and a whopping 106 duels all told at a febrile St Andrew's on Saturday night. No wonder Willock admitted: "There were some big challenges out there."

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In years gone by, Newcastle might have wilted in a dogfight versus the aggressive League One leaders. In fact, as a top-flight outfit, Newcastle have been eliminated from the FA Cup by sides from a lower division on 32 occasions.

Birmingham, Stevenage and Oxford United were among those teams who dumped Newcastle out of the competition in a previous era. Newcastle have even been knocked out by Sheffield Wednesday and Cambridge United since Howe took charge while Blackburn Rovers took the Magpies to penalties last season.

However, Newcastle dug in. Not only after conceding inside a minute - goals from Willock and Callum Wilson flipped the game on its head midway through the first half - but, also, when Birmingham equalised before the break.

That was the point when tensions threatened to spill over after William Osula took issue with a challenge from Jay Stansfield and momentarily went head-to-head with the Birmingham star. Osula was quickly surrounded by four blue shirts and Keshi Anderson and Ben Davies both shoved the Dane, which was the cue for Bruno Guimaraes, Dan Burn, Sean Longstaff, Tino Livramento, Emil Krafth and even goalkeeper Nick Pope to arrive on the scene and lead the forward away. Sean Longstaff took Osula aside for a quiet word and Eddie Howe urged his side to 'stay calm' at the interval.

"We were a little bit anxious and the game became a little bit emotional for us," the Newcastle boss said. "We didn't want flashpoints in it. We needed to be calm and control the game, and we did that much better in the second half."

That ability to stay calm spoke volumes, particularly when the tie only got more physical after the break. Marc Leonard was stretchered off after coming off worse in a 50/50 with Lewis Miley. Stansfield pulled Fabian Schar into the advertising hoardings. Willum Willumsson left Willock hobbling after catching the midfielder with a slide tackle as he skipped away from him. Ben Davies went into the back of Osula. Lyndon Dykes had not long been on the field when the substitute shoulder-barged Krafth to the ground before Willock's late winner.

However, Newcastle kept their heads. Just as the visitors did after conceding inside a minute.

The game had not long kicked off when Kieran Dowell's corner was headed back across goal by the unmarked Keshi Anderson and there was Ethan Laird to lash the ball into the net to give Birmingham City the dream start. Stunned Newcastle players were serenaded with a chorus of 'Who are ya? Who are ya?' from the jubilant home support - and it very nearly got even worse for the visitors.

Newcastle held firm against Arsenal, the set-play masters, but this much-changed side looked a little unsure from such situations and another delivery was headed back across by Christoph Klarer on the quarter-hour mark. Anderson caught it on the volley, this time, but Pope made a huge reflex save to push the ball away. It proved a big moment; Newcastle were level just a few minutes later.

The ball was fizzed to Callum Wilson inside the centre circle and the striker spun away from Ben Davies before bundling past Klarer and swinging the ball to the back post. There was William Osula to keep it in and cut the ball across to Joe Willock, who hit it first time. Although Bailey Peacock-Farrell managed to get a big hand to it, the assistant ruled that the ball had crossed the line.

The momentum of the game shifted and Newcastle were soon in front midway through the first half. Sean Longstaff sent Tino Livramento in on the overlap down the right and Wilson was there to finally hook the ball into the net at the third attempt after both Willock and Osula missed from point-blank range. Birmingham were not out of this, though.

Chris Davies' team have picked up more points from losing positions than any other side in the top four divisions in English football for a reason and the Blues came roaring back before half-time. Matt Targett could only head a deep cross as far as the edge of the area and there was Tomoki Iwata arriving on the scene to unleash a screamer that left Pope with no chance.

The game became stop-start and bitty after the break, but Newcastle found a way to win late on after Longstaff squeezed the ball across to Willock. The midfielder coolly drilled it through Peacock-Farrell's legs from close range to send the away end into raptures.

However, just as Birmingham came back at 2-1, the Blues did not know they were beaten at 3-2 and Pope had to produce another huge reflex save late on to keep a corner out with his foot. A whopping 12 minutes of stoppage time were added on, but Newcastle held on. Another route to Wembley remains open.