For the third time this season, Arsenal have suffered a scare over at least one of their key players during an international window, as former Brighton & Hove Albion man Trossard came off in the first half of Belgium's Nations League loss to Israel on Sunday.
The severity of the attacker's issue is yet to be disclosed, but he has failed to hit his previous heights in recent weeks, and Watts - speaking to Sports Mole - has suggested that a brief spell out of action might be just what the doctor ordered.
"It's definitely not welcome news," Watts said. "We're still waiting to find out the extent of the injury. The early sort of signals from Belgium was it was more of an impact injury than a muscle injury, so the hope is it's nothing that's going to keep him out for too long.
"Trossard hasn't been in the best of form of recent weeks. There have been lots of Arsenal fans who don't think he should be getting the minutes that he has been getting with his performances, but put that to one side, he's still a very crucial member of the squad.
"You look at the amount of goals he scored last season, arguably the best finisher in the squad even though he's not in the best of form right now, so you want him available and he offers you a lot of versatility as well.
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"You can play him on the left, you can play him centrally deeper. There's just so many different positions you can play Leo in, so he's a very handy member of this squad, so it is a blow. Hopefully it's nothing too serious, and who knows, if he does miss a couple of weeks it might even do him a bit of good.
"He can sit back, reflect, take stock a little bit and come back firing and ready to go, because his performances haven't been the best recently. He's definitely searching for a bit of confidence and a bit of form, so it might not actually be the worst timings, but I mean Arsenal will want him back quickly, no doubt about that."
Signed in January 2023 after Chelsea beat Arsenal to the signature of Mykhaylo Mudryk, Trossard immediately hit the ground running in North London and has proven his worth to Mikel Arteta as an impact substitute in particular.
However, the 29-year-old has only come up with two goals and one assist in 15 matches in all competitions this season, often having to fill in for the injured Martin Odegaard, and he has gone five games without directly contributing to a goal in the Premier League.
Trossard is one of four new concerns for Arsenal to take into account after the international break, as Declan Rice and Bukayo Saka both withdrew from the England squad after sustaining knocks in the 1-1 draw with Chelsea two weeks ago, while Ben White is expected to be absent for around eight weeks after undergoing surgery on a joint issue.
The Gunners have also been missing Riccardo Calafiori (knee), Takehiro Tomiyasu (knee) and Kieran Tierney (hamstring) in recent weeks, but Watts is confident that the former, Saka and Rice will all be given the green light to play on Saturday and believes that Arsenal's fitness situation is the best it has been all season.
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"We do expect them to be fit," Watts added. "I think Declan, there'll be a late decision taken on all of them, but there was certainly a hope at the start of the window that this break would do them good and they will be available for the Forest game.
"Calafiori, again, there is definitely a hope that he'll be fit for Forest, but if not Forest, very, very soon after the international break. It's not going to be long until he's back and I think Tomiyasu falls into the same boat there. For the first time really in a long time, the injury situation seems to be improving a little bit at Arsenal.
"The way things have gone this season, you've got to touch wood when you say that because it just feels like the next crisis is just around the corner when it comes to injuries. But it's looking better than it has done all season injury-wise for Arsenal.
"If you could get back after the international break and you have Saka and Rice available, Calafiori can come back to the left-hand side, and the one blow we've had recently is Ben White.
"But if you could just get Calafiori back and that would allow you to move Timber over to the right-hand side, then how big of a blow it is to losing someone like Ben White, it's still a very, very strong-looking back four that Arsenal have. That's before you factor Tomiyasu into the equation as well. Injury-wise, it's looking relatively decent despite the bad news we had about Ben White."
Arsenal went into the international break on a four-game winless sequence in the Premier League, a pitiful run of form that leaves them fourth in the top-flight table, nine points behind leaders Liverpool and only ahead of upcoming foes Forest on goal difference.