Dwight Gayle reacts to his injury and reveals his hope for a return at Newcastle
The striker was forced off with a hamstring problem after scoring his 20th goal of the season in yesterday's 2-1 win over Brentford.
United manager Rafa Benitez also lost Isaac Hayden and Vurnon Anita to injuries at Griffin Park.
The result saw the club return to the top of the Championship.
"Obviously, it was frustrating to come off, but the three points was the most important thing," said Gayle.
"I was buzzing that the boys ground three points out. There was a real buzz in the changing room."
Gayle, signed from Crystal Palace last summer, had a spell out with a hamstring problem last season.
And he could be out for a number of weeks.
"It was a hamstring," said the 26-year-old. "I had it last season as well.
"Fingers crossed it's not too bad, but we won't know the full extent of it for a few days. We'll see how it goes."
Newcastle struggled after losing game, and Lasse Vibe levelled early in the second half.
But substitute Daryl Murphy claimed all three points for Newcastle with a 79th-minute header.
"We knew what their team was about," said Gayle. "We were playing on the counter-attack, and I thought it worked really well.
"I was frustrated to come off in a game where it was perfectly made for myself."