The England forward landed awkwardly as he challenged Bruno Gaspar for a header early in the first half, with his team-mates showing immediate concern for his plight.
The Arsenal forward's career has been plagued by injuries, and this could be the worst of the lot. "The game in Lisbon was also hard but we won and now we can say those three points were very important".
The game only really opened up in the 88th minute when Jeremy Mathieu was shown a straight red for a foul on Pierre-Emerick Aubameyang as the striker raced through on goal.
Welbeck, who had netted more Europa League goals than any other Gunner over the course of the last two seasons, was dubbed the "Welbeck Express" after his clinical strike in the Portuguese capital. "We don't want it, but this is our profession".
Following on from the USA game, which will be the DC United star's only appearance, England will face off against Croatia in their final group match of the UEFA Nations League.
Rangers are now level on points with Spartak in an incredibly tight Group G, one point behind leaders Villarreal after the Spaniards´ goalless draw with Rapid Vienna in Austria.
"When you are playing football, when you are playing in competitive matches, it can happen". They saw it was a big injury.
AC Milan stayed just a point adrift of Group F leaders Real Betis after Suso´s second-half equaliser grabbed a 1-1 draw in Spain.
This latest setback comes on the day he was named in Gareth Southgate's latest England squad for the forthcoming games against the United States and Croatia.