The Gunners midfielder, on a season loan at Bournemouth, played in the 3-0 Boxing Day defeat at Stamford Bridge.
He admitted: “Chelsea look like champions at the minute — they are the best team in the league.
“Of course there is a long way to go so you cannot say they are definitely going to win it, but they look the strongest team.
“They are opening up a gap which is going to be difficult to claw back as the months go by.
“Chelsea look even more ruthless now, their players know the job in hand and are able to go out there week-in, week-out and change their game depending on who they are playing. That’s the sign of a top team.”