Jamie Carragher believes Arsenal still have to prove themselves if they are to be considered Premier League title challengers, reports Sky Sports.
The Gunners have had a fine start to the season, and impressed in their recent 4-1 demolition of Norwich City this past weekend.
However the north London outfit are without a trophy in eight years and the ex-Reds star has insisted it's difficult to back Arsene Wenger's team for league glory just yet.
The former England international believes tougher tests will arrive for the Gunners in the coming weeks and they will have to prove themselves in the big games.
Speaking on Monday Night Football, Carragher said: "We're sometimes scared to say it about Arsenal.
"If this was Man United or Chelsea or Man City then we'd all say they can win the league, but because they've gone so long without winning a trophy or challenging for the championship then we get a little bit scared of backing them for the title.
"But the form that they're in makes them look like the most impressive team in the Premier League at the moment.
"Before the Napoli game we thought it was a big test for Arsenal and they wiped the floor with Napoli.
"In a few weeks they play some of the big hitters. The thing that's often mentioned about Arsenal is that they always win the easy games, but what they've got to do now is win the big games. They need that mentality, physicality and intensity in their play.
"They've always beaten these types of teams. It's when they come up against the big teams - Chelsea, City and United - that I'm never confident they are going to win the game."
The Gunners currently sit top of the Premier League and have also been impressive in Europe so far this season.
Wenger's side take on Borussia Dortmund in the Champions League this evening and the German outfit certainly present a tough task for the Emirates outfit.