The Gunners have drawn Sparta Prague in their qualifier and Cesc said: "This is Arsenal and we simply have to be playing in the Champions League.
"If we don't make it then it would be a terrible blow for everyone - a disaster.
"We are used to being in the biggest competition in Europe. If we failed to qualify it would not be the same, right from the start of the season.
"We know we have to be ready and in good shape from the first week of the season. There can be no slip-ups.
"We learned last season that if you don't start the season well, you have problems right through to the end.