Per Mertesacker has warned Premier League defenders that Arsenal teammate Theo Walcott will only improve as he continues to adapt to his newly-acquired striking role.

Walcott has managed to sideline Olivier Giroud after enjoying a strong start to his stint as the Gunners' number nine, having spent much of his Arsenal career on the wing.

The 26-year-old has struck four times in six starts in all competitions, and Mertesacker says that his fear factor will increase week after week.

"It is a different position that what he played before on the wing," he is quoted as saying by The Mirror.

"In the centre he is always one against two, so he needs to find his way and his spaces and the pockets where he can be dangerous.

"That will always be more in behind [the defence], forcing [the opposition] to go back because they will always be scared, if Theo plays up front, of the space in behind."

Second-in-the-table Arsenal face top-flight new boys Watford away on Saturday evening.