Thierry Henry has claimed that keeping Alexis Sanchez fit this season is "vital" to any hopes former club Arsenal have of winning the Premier League title.

The Chile international has yet to hit the same heights witnessed during his maiden campaign in North London when scoring 25 times in all competitions.

Sanchez has started to return to something close to his best form in recent weeks, though, firing a hat-trick against Leicester City and twice against Manchester United prior to the recent international break.

A strike against Watford makes it seven for the campaign now for the 26-year-old, who Gunners legend Henry believes holds the key to Arsenal's aim of finishing top.

"I've said it so many times, but he's vital for Arsenal," he told Sky Sports News. "If he's fit I think Arsenal have a chance of winning the Premier League.

"If he stays injury-free and shows the desire and the commitment that he has for Arsenal in the way he plays then Arsenal have every chance of winning the title, but you need to keep that guy fit.

"He is that 'extra' type of guy that, when you're in trouble, he'll make sure you win the game. I don't want to copy a show on another channel, but he is the 'X-factor'."

Arsenal are joint-top of the table ahead of their trip to South Wales to face Swansea City this weekend.