And of course he's never had an entire year when he played at the level he did the first two months of the season, his game improved significantly last year.
His game improved for what, less than a quarter of a season (19 total games played before his injury)? After which he played 48 pretty wildly inconsistent games over the course of 4 months?
While I won't dispute the near-MVP level of play Rondo showed for the first 20 games he played this season, I do think that the next 48 games he played showed that maybe that was a hot streak, rather than an indicator of a baseline that he's capable of right now.
By the way, I just thought I'd add a little historical perspective to Rondo's "hot streak". In those 19 games he had 8 games of 15 or more assists. Since 1985 there are only about 23 guys that have had that many 15+ assist games in an entire season (I'm talking number of players that did this, players like Stockton and Magic did it multiple times). If you extrapolate Rondo's numbers to a half a season you'd get 17 games of 15+ assists. Only 6 players have had that many in an entire season in the last 25 years. He had 5 games of 17+ assists in those 19 games, only 6 players have had more than 7 such games in a season in those 25 years. So his "hot streak" was playing on a level that very few point guards in the history of the game are capable of ever reaching.
For more perspective, I looked at the leaders for games with 15+ assists in a season and compared it to scoring and rebounding. 15+ assist games look like they're about as common (for the leaders, again) as 36 point or 18 rebound games. So imagine a player that scored 36 or more 8 times in 19 games and averaged 33 points in that time or had 18 or more rebounds 8 times in 19 games and averaged 16 boards a game for that time, and then struggled with injuries for the rest of the season. What would you say was the scoring/rebounding baselines for those players?
Also, consider that, in spite of the fact that he struggled with injuries for most of the season, he averaged 11.2 assists with an assist% of 47 or so. If you check players that have played most of a season and done either of these you're looking at a dozen or so people ever. Back to the points/rebound comparisons, this happens as often as someone averages about 31 ppg or 17 boards. So if you had a player that struggled with injuries and still averaged 31 a game or 17 boards a game, what would you say about the baseline for what they're capable of playing? Because that's where Rondo is with his passing.