The Red Devils suffered an untimely injury scare with the in-form striker during the closing stages of their 2-1 Europa League win over Barcelona on Thursday, which sent them through to the last 16 4-3 on aggregate.
Rashford had to come off in the 88th minute due to an ankle knock, and he posted an image of himself trudging off the field accompanied by a bandaged emoji after the final whistle.
Fears were naturally raised of Rashford potentially not being fit to start the EFL Cup final or missing the game entirely, and Erik ten Hag did little to quell those concerns when asked for an update on Friday.
"We have to do investigations, medical, of course, yesterday we did. So straight after a game most of the time you can't say, you have to wait for a 100% diagnosis. So let's do the medical, the work, we have to wait," Ten Hag said.
However, as reported by The Mirror, Rashford was seen travelling with the Man United squad down to the capital for Sunday's final, although his status is still unclear.
The report claims that Ten Hag will likely have to make a last-minute call on the 25-year-old's participation while he also works around the absence of Anthony Martial, who is dealing with a hip problem.
Should Rashford miss out, Wout Weghorst can expect to lead the line with support from Antony, Bruno Fernandes and Jadon Sancho, in spite of his ineffective first half against Barcelona in midweek.
Man United have witnessed Rashford enjoy a period of glittering form since Ten Hag's arrival, with the striker netting 24 goals and setting up nine more in 37 appearances this season.
The England international scored in four successive EFL Cup games prior to the second leg of their semi-final against Nottingham Forest, where he laid on two assists in a 2-0 win.
None of Martial, Christian Eriksen and Donny van de Beek will take to the field at Wembley for Man United, but Newcastle have more pressing concerns regarding their team selection.
Eddie Howe is working without his two first-choice goalkeepers in Nick Pope and Martin Dubravka, the former of whom is serving a suspension following his red card against Liverpool last weekend.
Meanwhile, Dubravka is cup-tied after representing Man United in the tournament during his loan spell in the first half of the season, leaving Loris Karius and Mark Gillespie to battle for an unexpected start at Wembley.
Despite previously representing Newcastle in the 2020-21 tournament, Gillespie is expected to lose out to Karius, who has not played for an English club since his error-strewn display for Liverpool against Real Madrid in the 2017-18 Champions League final.
Victory for Man United on Sunday would win them their first piece of silverware since the 2016-17 Europa League, but it has nearly been 68 years since Newcastle last won a domestic trophy, going all the way in the 1954-55 FA Cup.