DeAndre Yedlin will undergo an X-ray on Thursday after Newcastle manager Steve Bruce said the U.S. defender suffered a suspected broken hand which "looks a mess" during their 3-0 Premier League defeat against Leicester City on New Year's Day.
American defender Yedlin had been introduced as a 45th minute substitute in place of full-back Jetro Willems, who was forced out of the St James' Park fixture with a groin injury.
Newcastle, who had lost Willems, Jonjo Shelvey and Javier Manquillo to injury before the start of the second half, were forced to play the final 40 minutes of the game with 10 men after Fabian Schar limped off with a hamstring problem five minutes after the restart. By that stage, Newcastle had used all three substitutes.
Yedlin suffered his injury shortly afterwards, but Bruce paid tribute to the former Seattle Sounders player for playing through the pain barrier for the remainder of the game, despite the problem with his hand.
"We lost four players to injury and might be without a fifth now because we think that Yedlin has broken his hand," Bruce said. "He played on manfully for the rest of the game, but I don't know how long he will be out for.
"We need to get him X-rayed, maybe also a scan, but it's a mess.
"In all the years I have been involved in the game, I have not known a crazy 15 minutes like that. From the goals we gave away to the four players going off injured -- it was ridiculous."
Newcastle face League One side Rochdale in the FA Cup third round on Saturday (stream live on ESPN +), with 10 players already ruled out due to injury.