I think some here are being a little overly dramatic regarding just how crucial this game is, unless of course you happen to be mistakenly discussing Orlando's point of view. For Orlando tonight is the series. Win and there's a glimmer of hope. Lose and it's over.
But for Boston? Sure every game is crucial but after the split in Cleveland they had the biggest playoff lost in franchise history and still won that series without going to seven games. And that extended amount of playing, compared to the other 3 teams participating in conference finals games, certainly didn't seem to effect their effort due to fatigue or focus due to fatigue. If anything it could be argued that they appear to be the most focused and strongest team still playing. So whether they win in 4 or 5 or 6 games, in my opinion, isn't going to effect the way they play in the Finals unless there is a major injury.
A Boston win is a confidence crusher for Orlando and makes Boston, to me the prohibitive favorite to win it all. A loss just shows they aren't a perfect team but still leaves them with HCA and the next game in their building with them playing with a chip on their shoulders. If they were going to lose any more games in Boston this year, I would bet this would be the one and I seriously doubt it will effect the outcome of this series or their overall play in general.