Manchester United’s afternoon went from bad to worse as England international Luke Shaw was forced off with an injury during the first half of their Premier League encounter with Crystal Palace. The left-back appeared to succumb to a foot problem just 23 minutes into the contest, leaving manager Michael Carrick with a significant tactical headache.Shaw was seen clutching his foot following a challenge from Palace full-back Daniel Munoz. The 28-year-old was unable to continue and was visibly distraught as he made his way toward the touchline. The sight of Shaw shaking his head as he left the field will be a major concern for the United faithful, given his history of recurring fitness issues throughout his time at Old Trafford. Shaw’s departure came at a pivotal moment, with Manchester United already trailing 1-0 following an early goal from Maxence Lacroix. It was an especially bitter blow for Shaw in a season that has seen him put his past fitness issues behind him to start every one of United's Premier League games.Carrick was forced into an early substitution, introducing Noussair Mazraoui to fill the void on the left flank. Despite the change, United struggled to find their rhythm against an energetic Palace side and went in at the break one goal down. However, Bruno Fernandes did draw United level from the penalty spot early in the second half, after Lacroix was sent off for a last-man challenge on Matheus Cunha.The club has confirmed that a full assessment will take place once the squad returns to the Carrington training complex. Whether the injury is a result of the collision with Munoz or a flare-up of a previous issue remains the key question. For United, the hope is that the early substitution was merely a precaution rather than the start of another lengthy spell on the sidelines for Shaw.Add GOAL.com as a preferred source on Google to see more of our reportingThere is a glimmer of hope for United in terms of the upcoming schedule. Due to a lack of European football and early exits from both domestic cup competitions, the Red Devils face a significantly less congested fixture list than their traditional top-six rivals. After Wednesday’s fixture against Newcastle United, the squad will have an 11-day break before they return to action at home against Aston Villa, providing Shaw with a potential window for rehabilitation.The medical team at Old Trafford will be working around the clock to assess the severity of the damage. Carrick will be desperate to have his first-choice left-back available for the run-in, as Shaw’s balance of defensive solidity and attacking output remains crucial to the way United transition from the back.