The Gunners finished fifth in the Premier League last term and failed to qualify for the Champions League for the first time in Wenger's reign, meaning they will play in the Europa League instead.
Wenger's men begin their campaign with the traditional Community Shield curtain-raiser against Chelsea at Wembley on Sunday.
And the Frenchman feels investment from all of last year's top six, aside from local rivals Tottenham, means it is tough to predict who will be lifting the Premier League trophy at the end of the season.
"I would have loved to play in the Champions League, but we have to deal with the reality that we are not in it," Wenger told reporters on Thursday.
"For us it is a good opportunity to focus completely on the Premier League, but anyway I would say that the Premier League has in my opinion taken over from the Champions League interest-wise.
"It happened sometimes that we rested players in the group stage of the Champions League to prepare for the next Premier League game, because every Premier League game is so difficult.
"It's very difficult at the moment to evaluate the real forces in the Premier League. Manchester United have bought, City have bought many players, Liverpool have bought, we have bought, Chelsea have bought, Tottenham have a young group that is together for a long time.
"It's very open and it's very difficult for me to predict exactly what will happen."