CHICAGO - The Celtics arrived here last night with six straight wins and a locomotive load of momentum. The Bulls? Oh, just the worst team in NBA captivity.

Against a Chicago outfit that was 3-15, the Celtic streak sprang a leak. Former Celtic Ron Mercer hit a 17-footer and a free throw for the game's last points and an 87-84 shot to the Bostonian ego.

As Sammy Davis Jr. might have put it: ``Ouch . . . and I mean that, babe.''