Out of the title race, two Alexis Sánchez goals took Arsenal back up to third place on Thursday evening: what if he’d been on form all season?

The Chilean missed almost two months in the winter and, after such a busy summer on international duty, has struggled for top form for much of the campaign.

Either side of his injury, Alexis had runs of five Premier League starts without scoring. He has returned to the right wing and rediscovered top form but Mertesacker has been left wondering what may have been if Arsenal’s star man hadn’t suffered an injury back in November.

Arsenal won five of eight Premier League games without Alexis in the side – could it have been more?

“Obviously, if he is on the pitch, he always creates space for other players because he draws so much attention and that is the key to any team,” the German said in an interview with the Guardian.

“He is a key member of our team and if he is fully fit, he makes the difference and that is always the case.”

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Alexis scored twice on Thursday to win Arsenal all three points against West Brom. GLYN KIRK/AFP/Getty Images)

Alexis may have struggled for form in much of the campaign but, moving to the right wing in recent weeks, he looks reinvigorated. Six goals in as many games haven’t helped Arsenal to more than three wins – too few at a crucial time in the season – but have been crucial nonetheless.

Once more, the 27-year-old looks unplayable.

“Over the whole season, normally we need him healthy. He is the type of player who makes the difference and even when he is in Chile playing two World Cup qualifiers, he will be back on track in the right time.

“He is that type of player who gives everything to the team. Those team members are well appreciated.”

That was evident on Thursday, when Alexis looked in top form against a poor Tony Pulis side. Two goals won the headlines and the game but the Chilean did much more, creating chances and hassling the West Brom players in possession.

Now on 16 goals for the season, 12 in the Premier League, Arsenal fans are seeing the best of Alexis again.

If only he’d been fit for the whole campaign.