Capped 35 times by Wales, the 33-year-old Sweeney moves to Exeter Chiefs for next season after stints with the Newport Gwent Dragons and then the Blues.
And although he won't be at the capital city region next season, Sweeney says Phil Davies' side have the talent coming through to bring success.
"With a couple of signings, I'm expecting the Blues to come back a lot stronger next year," he said ahead of Saturday's PRO12 clash with bottom side Zebre.
"We lost a lot of experienced, quality players and there's been a massive turnaround in terms of age and experience.
"Phil's taken on a group of youngsters and he's perfect for that kind of job. He's really enthusiastic and put a lot of faith in their ability."
Sweeney has seen first-hand the progression of some of the Blues younger players - Rhys Patchell, in his own position of outside-half, an example of a player enjoying an impressive start in regional rugby.
And with the likes of Patchell and Harry Robinson supplemented by the signings of Welsh internationals Gethin Jenkins and Matthew Rees for next season, the future for the Blues looks bright.
"Phil has said we want to finish the season on a high and build momentum going into the off season," Sweeney added.
"Everyone wants to finish on a winning note so we'll certainly be looking to do that against Zebre at home. It's a game we've targeted for a five point win, not just a normal win. We haven't been quite as good as we would have liked to have been at home so we want to send the fans off with a win."
The clash with Zebre promises to be an emotional occasion for Sweeney, as well as centre Jamie Roberts, who also plays his last home game for the region on Saturday.
The Blues finish their season with consecutive away games against the Scarlets and Ulster following the meeting with the Italian side.
And after five years with the region, winning both the EDF Energy Cup and Amlin Challenge Cup in the process, Sweeney wants to go out with a bang.
"I've had some great times here so I think it will be a bit emotional on Saturday," he said.