The 24-year-old limped out of the Magpies' game with Bournemouth last week after just half an hour.
The 24-year-old had only just returned to action after a month out with a different hamstring problem (via Shields Gazette). And while he came through the Magpies' clash with Stoke at the start of the month unscathed, he had to be taken off just after the half-hour mark during the club's home defeat to Bournemouth in their most recent game.
While the Wales international will only miss three games if he does have to sit out the entire next month, there is no doubt that they are three huge fixtures that the club could have done with having one of their most consistent performers available for.
On Monday, Newcastle are set to take on Leicester City at the King Power Stadium. And if facing an away trip to the league leaders wasn't daunting enough, they will then take on Sunderland in one of the most important Tyne-Wear derbies in recent memory before facing Norwich at the start of April.
With both of the latter two games pitting United against their two main rivals in the fight for Premier League safety - Norwich are level on points with the Magpies, while Sunderland have one more than the pair - the next month could prove critical to the team's chances of beating the drop.