The star duo left the Liberty Stadium for Everton and West Ham respectively in the summer, and although signings were made with the money, Bradley does not think they have been properly replaced.
The Swans have struggled in the Premier League this season and Bradley says that is partly down to the fact that two influential players, on and off the pitch, left the club.
"All Swansea supporters know that they were important players last year," Bradley told BBC Radio 5 live. "When players like that leave, not only do you lose the talent they had on the field, but both of those players were strong figures in the dressing room."
Bradley has also confirmed that everything possible is being done to strengthen the squad with one or two players when the transfer window re-opens.
"I don't think we need surgery but, like many teams, I think we need to use January to improve ourselves," he added. "We've had some good discussions already and without a doubt I think we can add a couple of important pieces."