The defender believes the club landed a bargain when signing Downing from Liverpool and he is looking forward to him linking up with his former team-mate Carroll.
It will not be this weekend though, as West Ham will still be missing Carroll, who is out with a heel injury, for Saturday's trip to Newcastle, but Collins is thrilled by the prospect of the former Liverpool pair reuniting.
He said: "The thought of him playing with Andy is great. They played together at Liverpool and they get on well off the pitch as well.
"They are both from the north east so have that certain understanding, which could be great for us."