Per Mertesacker insists Arsenal will focus on Blackburn in the FA Cup on Saturday, just 72 hours before German giant Bayern Munich arrives in north London for a last-16 Champions League first-leg clash.

Arsene Wenger's side is targeting a first trophy since it won the FA Cup in 2005 and the meeting with second-tier Rovers coincides with an improved run of form that has revived its bid for a top-four finish in the Premier League.

But Mertesacker, the Arsenal centerback, has warned his team-mates they cannot allow their focus to be distracted if they want to progress in the domestic competition.

"We still have an important Cup game on Saturday first. We absolutely want to advance in the FA Cup, that is why the preparations for Bayern are not that intense yet," said the Germany international.

"However, beginning on Sunday the preparations for Tuesday's match will be extreme. Bayern are doing superb this year and that is a big challenge for us, but we are looking forward to both legs."

The prospect of facing Bayern means Arsenal boss Wenger is expected to make changes for a Cup tie with a Blackburn side which has made great strides since Michael Appleton succeeded Henning Berg as manager.

Jack Wilshere (thigh) and Laurent Koscielny (calf) are struggling for full fitness while Thomas Vermaelen is likely to be on the bench.

"Wilshere is having tests," Wenger said.

"He is looking better. He is still a doubt for Saturday. He's got a kick on the thigh.

"Koscielny is a problem," the Frenchman said. "He has a test today (Thursday) and tomorrow (Friday) exactly like Wilshere.

"Vermaelen is looking quite good and is possibly back for Saturday. He should be in the squad."

Midfielder Abou Diaby is available but right back Carl Jenkinson is suspended following his dismissal in last weekend's victory at Sunderland.

And Theo Walcott, the Arsenal and England winger, added it was vital the squad players drafted in to face Blackburn maintained the momentum.

"A lot of players are back from international duty and need a bit of a break," said Walcott.

"Some may be rested for the FA Cup game, but that's just as important as we want to go far in that competition."