Manuel Pellegrini's men were beaten 1-0 at Turf Moor in the Premier League on Saturday - their third defeat in four matches in all competitions.
That run started with the home loss against Barca in this competition and, with a turnaround at Camp Nou unlikely, Pellegrini appeared to be getting his excuses in early.
"Manchester United in all of that great era under [Alex] Ferguson only won two Champions Leagues," he said. "Real Madrid went 32 years without winning the European Cup.
"It is important to be there in the later rounds but you can't think that not being there is a disaster."
"You can talk about tactics and technique but if you go a man down against Barcelona, you're put in a terrible position," he added. "It is not a disgrace to get knocked out by them.
"Their squad, if it is not the best in the world, it is the second best. No other team can put together Leo Messi, Neymar and Luis Suarez but I want to play them with 11 and if they knock us out then let that be because they were better than us."
But speaking earlier this week, coach Luis Enrique said: "This will be a very nice week with two games in front of our fans, but it is not the most important.
"We're going into the Clasico as leaders and in perfect form. But first we have to focus on City because qualification is at stake. Then we'll see what happens at the weekend."
Barcelona's Martin Montoya sustained a fractured cheekbone in a 2-0 win at Eibar on Saturday, while Sergio Busquets (ankle) missed training this week.
