I don't know. I've begun thinking that any NBA team can beat any other NBA team on any given night. It's unlikely that the Knicks or Magic can beat the top tier teams but I watched on as the Sixers almost topped the Thunder in regulation last week and could have had the game in OT also.
If your question is a compliment to the Cs, then yes, I do think the Celtics are a team they can test themselves and evaluate others on. This is a decent team. Better in a variety of ways than the team that began the year with Rondo and Green. This team has shown that they can put up great quarters against some of the best teams one day and get blown out by the same top tier teams the next. I think the Celtics are a scary team to face if you're on the edge of playoffs in either conference.
The Suns beating the Nets last night was huge for a Celtics playoff push, just as the Celtics beating the Pelicans was big for the Suns and the Thunder. I've been so impressed with this team as of late that I'm actually rooting for them to meet the playoffs...even if they're swept first round. If they don't make it to playoffs I'm still happy though, betters our chances of grabbing a C in the draft.