Monaco qualified for the Champions League quarter-finals, for the first time since 2004, and went through on away goals after a 3-3 aggregate result against Arsenal in a thriller at the Louis II stadium.
Arsene Wenger, who was returning to the club he coached between 1987 and 2004, was left a frustrated figure after goals from Olivier Giroud and Aaron Ramsey were enough for a 2-0 win on Tuesday night but not enough to send the North Londoners through.
"We knew it would be very difficult to score that many goals," a philosophic Wenger told BeIn Sport after the tie.
"We weren't realistic enough in our approach and we should have been up by more at half-time.
"At the end of the day, we paid for our performance in the first leg. Monaco were playing at home but didn't have a shot on goal. We were very close but they surprised us in the first match because subconsciously we were too sure of ourselves," added the Frenchman.
"It's not a question of if we deserved to go through but of being realistic and we made too many errors in the first leg.
"We have to congratulate Monaco for their place in the last eight as they defended really well. They qualified so 'Bravo'! We are on the right track and played the match we had too.
"The last three months we haven't lacked in anything except our performance in the first leg.
"We have a superb spirit and great qualities," added the Frenchman, who helped Monaco win the 1988 French title, the 1991 French Cup and also guided the team to the 1992 Cup Winners' Cup final where they lost against German side Werder Bremen.
Monaco vice-president Vadim Vasilyev hailed a great night in the club's history.
"It's a great night for AS Monaco and it's been 11 years since the 2003-04 season when the team reached this level. Arsenal played a great match but we stayed solid defensively although the final minutes were very difficult.
"It's great happiness but we play every match to win. In the changing room, the players were very proud to qualify but it's true we didn't celebrate like we did after winning the first match." he added.
Arsenal were attempting to become the first team in Champions League history to overcome a 3-1 first-leg defeat at home but came up agonisingly short.
Constant pressure for 90 minutes, could have, provided more than two goals on another day, but the excellent Danijel Subasic turned in his second straight world class showing to play a decisive role.
Ramsey, who came on as a substitute and played a key role in putting Arsenal into position to qualify, explained there was reason for deep regret after the defeat.
"We've always gone out to Bayern Munich and Barcelona at this stage but no disrespect to Monaco, we thought we'd have a good opportunity to qualify but we gave ourselves a tough test from the first leg.
"It's nearly again, but it's not enough." said the Welshman.
Monaco become the second French team to go into Friday's draw, following Paris Saint-Germain's equally dramatic victory over Chelsea last week and will be joined by Real Madrid, Bayern Munich, Porto and Atletico Madrid ahead of Wednesday's matches.
Source: AFP