Mertesacker reacts during an English Premier League football match on December 1, 2012
Per Mertesacker insists Arsenal will focus on Blackburn in the FA Cup on Saturday, just 72 hours before German giants Bayern Munich arrive in north London for a last 16 Champions League first leg clash.
Arsene Wenger's side are targeting a first trophy since they won the FA Cup in 2005 and the meeting with second-tier Rovers coincides with an improved run of form that has revived their bid for a top four finish in the Premier League.
But Mertesacker, the Arsenal centre-back, 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 who have 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 on Thursday and Friday," 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 added. "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."
Meanwhile Appleton is hoping his side can surprise the Gunners.
The last time Rovers visited Arsenal's ground they were beaten 7-1 in the Premier League in February 2012 before being relegated to the Championship at the end of the season.
After investing in players in pre-season, including £8 million striker Jordan Rhodes, Blackburn and Appleton, their third permanent manager of the campaign, are under pressure to make an immediate return to the top flight.
They sit six points off the play-off positions and Appleton is relishing the FA Cup tie as a game with no pressure.
"I think it is certainly a weekend off in terms of the league fixtures," said Appleton. "With the FA Cup game it does give us an opportunity to enjoy the match more than we would in a normal league game.
"In saying that, I don't think you can relax too much going to the Emirates against an Arsenal side.
"Three days after they play us they are going to play in a Champions League tie against a fantastic German side in Bayern Munich, so we know that the task is going to be very difficult.
"But we'll go there, we'll have a go and see if we can make a surprise."