Holders Bayern Munich kept their hopes alive of becoming the first team to retain the Champions League trophy while Atletico Madrid also progressed to the quarter-finals of this season's competition on Tuesday.
Bayern - who have reached the final of the past two Champions League campaigns - were held 1-1 in Munich by Arsenal, but just as they did last year against the same opposition at the same stage, the Germans went through, this time 3-1 on aggregate.
However Bayern's joy at going through was somewhat soured after Arsenal coach Arsene Wenger accused Dutch wing Arjen Robben of diving throughout the two legs.
"Robben dived tonight (he was told to get up by the referee when he went down early in the second-half in the penalty area) and he dived in the first leg," said Wenger.
Robben, who won a penalty for Bayern in the first leg which saw the Arsenal goalkeeper sent off, was dismissive of the remarks.
"Great managers don't need to resort to claims like that. I don't want to have to defend myself against remarks like that," he said.
Guardiola, who has won the trophy twice as coach of Barcelona, looked annoyed when told about the comments.
"The best team won over the two legs that is what happened," he said.
Atletico - who are the surprise package of the competition this season as well as in the La Liga title race -- reached their first Champions League quarter-final since 1997, when their present coach Diego Simeone was in the side, with a far more emphatic 4-1 win at home to Italian side AC Milan, to prevail 5-1 on aggregate.
It left Italy without a side remaining in the competition as Napoli and Juventus went out in the group stage.
Simeone, a former combative Argentinian international midfielder who was capped over 100 times, said he was proud of his side and tried to play down expectations by saying Atletico were very much the underdogs still.
"It is a very nice moment, after such a long time," said the 43-year-old.
"But we are still at the beginning of the knockout stages, and we must continue to get better.
"A difficult and dangerous quarter-final awaits us and we will have to recuperate and continue on the path we are following.
"There will be seven great sides in the last eight and one which will be very enthusiastic and capable of upsetting the others.
"As for Diego Costa he continues to progress, he has great physical strength and presence. He reminds me of some of the great strikers."
In Munich Bastian Schweinsteiger opened the scoring for the hosts - his first goal since October - before Lukas Podolski equalised for Arsenal against his former team, just as he had done in last season's first leg match.
The hosts could have won the match itself right at the end but Thomas Mueller's penalty was saved by Lukasz Fabianski.
In Madrid the result never looked too much in doubt, once Diego Costa got the opener after three minutes, despite former Real Madrid star Kaka levelling halfway through the first-half.
Turkish international Arda Turan restored the one goal lead before the break with a half-volley that took a wicked deflection and Raul Garcia and Costa added two more in the second-half, the latter taking his tally in all competitions this season to 29, including seven in the Champions League.
Milan's rookie Dutch coach Clarence Seedorf said the second goal had been the killer for his side, who are a shadow of the great Milan sides he was when he was a player.
"For a game and a half we saw a very good AC Milan side," he said.
"The team responded with courage from a great goal by Costa until their second goal, that was a very tough blow to overcome.
"The players tried to react, but they weren't able to."