I remember Eddie House being a big part of that team. His playing time fell off a cliff in the playoffs (I don't recall why partly because of Sam Cassell, I guess) but during the season the offense was always better with his on the floor. He was also instrumental in Game 4.
Rondo might've been the 5th most important player on that team but I think there is a clear Tier 1 (the big 3) and then a huge drop and a Tier 2 of Perkins, Rondo, Posey, House, and Allen (during the regular season). In the playoffs, House and Allen kind of fell out of the rotation but House still had the same mpg average as Perkins in the Finals.
Rondo was important but the gap from 3rd and 4th was much bigger than the gap between 4th and 8th, in terms of "most important".
I concur with this assessment. Folks tend to blur the 2nd year Rondo of that title season, who was more of a 'strong supporting cast' with the more individually dominant star PG Rondo of the following 3 seasons.
A telling stat that shows the difference in importance is Rondo's AST%, the percentage of his teammates shots that he assisted. Rondo's first two seasons, he assisted 26.3% & 28.2% of his teammate's shots. Those are solid percentages, typical of a PG, but nothing super notable. The team still relied heavily on Pierce, KG, Cassell & others to dish assists during that season. Rondo totaled 393 assists that season, but Pierce was not far behind with 363.
During the 2008 playoffs, Doc increased his reliance on Rondo's passing when he was on the floor, bumping his AST% up to 36%., but Pierce, KG and others still dished a large volume of the assists as well. Rondo's overall Win Share value during those playoffs was still only 5th on the team and his accrual rate (WS/48) was 7th. So he was a valuable part of that team, but hardly one of the top, most critical pieces.
In subsequent years, Rondo took control of a much larger share of the offense. In his 3rd season his AST% was 39.7% and then, over the next 6 seasons it was never lower than 43.7%!!!
Rondo had a very good season in terms of Win Share value during the title season, posting 7.2 WS. But it was his next two seasons, when that leaped to 9.9 and 9.6 WS, respectively, that he played like an all-star player. After that, his win shares declined rather rapidly: 6.6, 4.9, 3.2, 1.1 & 1.6, sequentially, in his last years in Boston.
This is where Rondo's criticism of Thomas rings kinda hollow. Because in the years when Rondo was actually playing his best basketball of his career, when he was legitimately one of the top players on his team, he didn't win any titles either.