The midfielder was forced off in Monday night’s 2-0 defeat to Arsenal, his former club.
Hayden felt his hip during the first half at the Emirates Stadium.
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The defeat left the club 14th in the Premier League, and seven points above the relegation zone, with six games left to play. And Hayden, a fixture in Rafa Benitez’s midfield since the turn of the year, is being assessed ahead of Saturday’s home game against Crystal Palace.
“I don’t know how it’s going to react until I see when I return to training really,” said Hayden. “It’s just one of those things where I took the ball during the first half, and I just felt a little bit tight around my hip area.
“I wanted to play on and I said I wanted to carry on, but then during the second half I just found it really hard to move and so the manager took me off.”
Newcastle created very little against Arsenal, who moved up to third place in the Premier League after what was their 10th successive home win.
“It’s always difficult when you play Arsenal at there place, and there are always pockets of space which are just so difficult to cover,” said Hayden. “They had players almost everywhere in certain positions, so it was difficult to cover all of those gaps. During the first half, I still thought we had our chances – it was just the final ball that was lacking.
“If we’d have had that final ball, we could have caused a few more problems.
“But, coming away to the Emirates, where only Man City and a couple of other teams have taken points from them, we knew it was going to be a difficult task. We just didn’t cause them enough problems in attack.”
Hayden joined United from Arsenal, his boyhood club, in the summer of 2016.
The 24-year-old said: “The football club means a lot to me – I’ve been an Arsenal fan my whole life – and I lived the dream because I got to play for them.”
United last won away from home in mid-December.
“You’re going to have times where you’re going to play well at home, and well away,” said Hayden. “We had a period where we couldn’t buy a win at home, and now it’s the other way round – it’s just the Premier League.
“Look at the teams we’re playing against – they’re all very good teams. It’s always difficult to win away from home, but we’ve come on leaps and bounds in 2019 so far, and we’re not going to be a Man City where we win every game or get points every game, and against Arsenal we’re disappointed with how we played.
“We’ll find some positives to take though, and not just focus on the negatives.”
United are three points from Benitez’s 38-point safety target.
“Everyone’s going to have their opinion on it, but in my opinion, until you reach 40 points, that’s the guaranteed mark really for safety,” said Hayden.
“Until it’s mathematically impossible for you to go down, or until you go above 40 points, you can’t really take your foot off the gas.”