Lucas Perri admitted his penalty preparations proved redundant despite helping Leeds United to a shoot-out victory over Birmingham City in the FA Cup.

Patrick Roberts' late deflected finish cancelled out Lukas Nmecha's thunderous second-half opener before penalties were required to separate the two sides in the fourth-round clash at St. Andrew's.

Perri delivered in Leeds' moment of need, first diving low to his right to deny Tommy Doyle before watching Roberts blaze over as Daniel Farke's side trumped their opponents 4-2 in the shoot-out.

But the Leeds goalkeeper says his research for Birmingham's spot-kicks went to waste, having been unable to identify the takers and, instead, having to rely on his instincts.

"Unfortunately, for the first two penalties, since they didn't have their numbers on their shorts, it was difficult for me to see," Perri told TNT Sports.

"And the third one, we didn't know exactly [where he would shoot, so I used] instinct. I am happy to help the club."

Perri has fallen out of favour with Farke, who criticised his goalkeeper's efforts in a 4-3 defeat away to Newcastle United in the Premier League last month.

The former Lyon man has since been named on the bench for six games, with Karl Darlow preferred before Farke opted to rotate for Sunday's FA Cup action.

His change seemingly paid dividends as Perri produced an excellent first-half stop to thwart Jay Stansfield, before Leeds won a penalty shoot-out for only the second time in their last six attempts. 

It was also only the second time they had contested one in this competition, after a 4-2 loss to Wolves in a third-round replay in 2005-06.

And team-mate Sean Longstaff, who scored the winner from 12 yards to settle the clash, was delighted to see Perri step up.

"Lucas was excellent. He was massive in the shootout, but [also] in the whole game. He made two or three massive saves," the former Newcastle midfielder said.

"We ground out a result. It's never pretty in the FA Cup. Any time you are drawn away to a team in a lower division, people expect you to just rock up and win, but that's never the case. They were excellent.

"I am really happy for Lucas. It's been, not a tough time for him, but up and down."