This has been an interesting debate. I'm still not sure why none of the posters who claim that Irving is a superior player to Rondo, or think that Rondo can't be the best player on a contending team, refuse to take into consideration the way that Rondo has led this team deep into the playoffs over the course of the past four seasons.
Rondo has already been the best player on a team that made it to game seven of the NBA Finals and game seven of the Eastern Conference Finals.
He's shown over the course of the last four seasons that he steps up his game in the playoffs. Some seem to take this as a negative against Rondo. To me, this is a distinct positive. I also don't think it's purely a cause of him "bringing it" more in the playoffs, but also a product of what a cerebral basketball player he is. When he plays the same team four or more consecutive games, he learns tendencies, he adjusts, he gets better. He's the type of player who is always thinking ahead to the next play or the next game. The playoffs--where you face the same teams multiple times in a seven game series--are geared to benefit a thinking player like Rondo.
To date, I have no idea how Irving will perform in the NBA playoffs. He hasn't been there. Rondo has been there a lot, and excelled at the highest level. That's worth a lot to me. I'm surprised that it's not worth more to others.
A case can be made that Rondo wasn't our best overall player on either of those teams in the playoffs.
And for all of the talk that Rondo is so much better in the playoffs, the numbers don't really bear it out at all. He just plays more minutes in the playoffs.
Let's look at 2009-10 for an example, the year you called him the best player on our Finals team.
His regular season stats, per 36 minutes - 13.5 PPG, 4.4 RPG, 9.6 APG, 51% shooting, .156 Win Shares (per 48 minutes), 54% true shooting, 52% eFG%.
His postseason stats, per 36 minutes - 14.0 PPG, 4.9 RPG, 8.2 APG, 46% shooting, .131 Win Shares (per 48 minutes), 50% true shooting, 48% eFG%.
So his "stepping up in the playoffs" in 2009-2010 actually saw him arguably play worse. He scored half a point more and got half a rebound more per 36 minutes, while losing 1.4 assists and scoring less efficiently. This is all not to mention that his worst round of all was in the Finals, with some pretty grim looking box scores.
There are seasons where his playoff numbers are slightly better, there are seasons where his playoff numbers are slightly worse. Overall, it's pretty much a draw. Rondo's "clutch" attribute is a myth. He's an All-Star caliber player in the regular season and an All-Star caliber player of equal talent that plays more minutes in the postseason.
To the bolded statement, I'd say, no, he hasn't.