Roberto Martinez believes Everton's clash with Arsenal on Saturday could be their greatest test of the season.
Arsenal recovered from defeats in their opening two Champions League fixtures to beat Bayern Munich 2-0 on Tuesday.
It was a deserved result, according to the Everton boss, who thinks Arsene Wenger's side will provide them with a huge task.
"We are facing an Arsenal team that I watched against Bayern and I don't think it's a coincidence that they won," Martinez told The Telegraph.
"They were very worthy of the win. They are a very complete team at the moment and I think this will be as big a challenge as we will face all season."
Everton have never won at the Emirates Stadium, with their last victory away at Arsenal coming at Highbury back in January 1996.
Martinez is unsure why the Merseyside club have been unable to replicate that result since, insisting they must overcome psychological barriers to get three points on Saturday.
"I don't know. I've been thinking the same and it's difficult to give a straight answer," he added.
"Obviously, two years ago we were very good there and deserved to win the game but ended up drawing 1-1, and you're thinking about something a bit further than just the game itself in terms of the psychological edge you might need to go to places like Old Trafford and the Emirates and believe that you can win.
"On Saturday we have to react to our performance last weekend [a 3-0 defeat to Manchester United].
"We cannot just afford to be facing Arsenal and that could narrow things down in terms of not carrying that baggage of not being able to win there for a long time."
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