Tinsley, if he's playing like he can, would be an upgrade over House and Pruitt, but not necessarily an upgrade over Cassell if Cassell is playing like he did 2 years ago.
It'd be nice to see what Cassell can do so we can gauge what we need.
Maybe Ainge and Doc know and just don't want to show anyone yet.
Tinsley wouldn't take minutes away from House; the idea would be to have a legit PG on the floor so Eddie can play off the ball. Tinsely's a little bigger than House; if he's inclined to D up (if he's not, don't pick up the phone), you might see him defend the SG and let Eddie pester the point. If anything, I bet you'd see Tony Allen's minutes get cut and the Pruitt experiment shelved until next year.
Cassell... I don't know, man. If he's playing like he did most of last season, he makes a great coach.
I'm not sure that's the case. I know everyone talks about freeing House to hit shots off screens, and that works fine in the regular season, but I don't think that works so well when we make the playoffs and we have to defensively contend with the likes of Joe Johnson, Hedo Turkoglu, LeBron James, and Rip Hamilton. I have a feeling come playoff time that Tony Allen is going to get the backup minutes at the 2/3, which means that House is going to have to play point guard or sit on the bench. Personally, I'm OK with the latter if we have a real PG out there.
I've thought all along that we're missing a legitimate, defensive-minded wing player (someone like, say... POSE!

). I'm not sure that I want Tony Allen to be that guy, though. The playoffs mean matching up with better wing players, but they also mean that mistakes are magnified. We're so evenly matched up with Cleveland, I wouldn't be surprised if every game in a series was decided by less than 5 points; Tony Allen can lose 5 points for us before you can call a timeout. My opinion only, but I think playing Eddie at the 2 for 15 minutes a night results in more net positive things than playing Tony out there.
Tinsley's not the answer to fix the need for another defender, but I'm not sure who's out there that is.