A hat-trick from Inter's Brazilian striker Adriano gave Inter a 3-1 win on the night, a 4-2 aggregate victory, and ensured that Porto became the first defending champions to fail to make it to the last eight in the subsequent campaign.
"There are so many different players that they are totally different teams and you can't make a comparison," said Couceiro.
"The only thing this side has in common with last season's is their name," he added.
The Portuguese side, who beat Monaco in last season's final, surprised many by their triumph but lost coach Jose Mourinho to Chelsea and saw many of their top players depart, such as Brazilian Deco now with Barcelona.
Although not in the same class as Mourinho's side, Porto caused Inter some problems in the second half after they made it 2-1 with a goal from Jorge Costa.
"We knew at just 1-0 down we could be back in the game with a single goal but after Adriano's second we were forced to go at them and of course that left us exposed at the back," said Couceiro.
"The game was decided by errors, not just in defence but throughout the team and in the end we simply didn't create enough ourselves," added the Porto coach.
Porto striker Benni McCarthy was also left to rue his side's exit.
He told Sky Sports: "We were not as confident as we were supposed to be, we knew we had to start off great after drawing 1-1 at home and we gave away an early goal.
"We had to work twice as hard to get back and after that and it became a bit of a Mission Impossible, but we worked hard and all credit to the guys. But it can be very tough against Italian teams.
"They defend well and we weren't as good as we could have been tonight."
HARD WAY
Inter coach Roberto Mancini admitted his side had done things the hard way.
"We did everything we could to make things difficult for ourselves. Having scored early we then pulled back and didn't create much during the first half except on the break.
"We were better after the interval, though we should have been more careful on that corner when Porto scored. When you concede a goal to go 2-1 up with 20 minutes left it's only natural that you feel a bit of fear.
"It was a good evening though and I am really pleased for the fans who deserved a night like this. I am particularly happy that Adriano is back scoring again -- he really deserved to get through his difficult moment," said Mancini, referring to the lack of recent goals from the Brazilian who had scored just once in this calendar year.
MAKESHIFT DEFENCE
Without the suspended Colombian centre-half Ivan Cordoba and left-back Giuseppe Favalli, Inter were forced to play a makeshift defence with Sinisa Mihajlovic and Marco Materazzi alongside each other in the middle for just the second time.
"The defence did very well and deserve some credit as they hadn't played much together and apart from the lapse of concentration for their goal gave away very little," said Mancini.
Inter's Argentine midfielder Juan Sebastian Veron was delighted to be in the last eight as he rebuilds his career in Italy following disappointing spells in England with Manchester United and Chelsea.
"I've waited a long time for a night like this. During the past few seasons I haven't played as much as I wanted, so to play in a packed San Siro like this is something really special," he said.
Asked about Adriano's performance, he said: "It was important for the club and also for us, because the season hasn't gone exactly how we would have liked.
"In the dressing room we're all happy. Outside, unfortunately, there are people who like to speculate on who wants to stay and who wants to go. We're at a very important phase of the season and it's a big boost to have him scoring again."
