"We're not scared of Watford. We have got to go out there and win," said Sinclair.
"If we can beat Watford, I think it will give a good indication that, when it comes to this division, we are not that far away."
The former England winger was speaking ahead of tonight's Championship clash at Ninian Park.
City have so far lost both home Championship games and tonight's visitor look stronger than previous visitors Stoke and Coventry.
"It's going to be our biggest test. Up until now we've faced sides we believed we could beat if we were on our game, but Watford will come here believing they can beat us."
Kick off at Ninian Park is at 7:45pm.