In 2001-02, Jose Theodore had a career year, posting a .931 save percentage in 67 games played. The Montreal Canadiens were a weak team, ranking 19th in the league in scoring (2.52 goals per game) and 27th in shots allowed (31.7). Montreal made it to the playoffs anyway, edging out Washington by 2 points for the 8th seed, mostly because of Theodore's outstanding play. At the end of the season, Theodore took home the Vezina Trophy winner as the league's top goalie and also won the Hart Trophy for league MVP. His season was an example of how great goaltending can make a big difference for a mediocre team.
In 2003-04, Roberto Luongo had a similarly fantastic year, with an identical .931 save percentage in 73 games played for the Florida Panthers. The Panthers ranked 23rd in scoring (2.29 goals per game), and 29th in shots allowed (34.0). They finished with 75 points, 16 short of the playoffs. Despite his excellent season, Luongo finished 3rd in Vezina Trophy voting, and 6th in MVP voting. Luongo played as well as Theodore did in more games and on an even weaker team. Yet he did not get the same recognition. In the view of many observers, if he was really that good he should have found a way to get his team into that 8th spot, as Theodore had done.
The problem is that it is doubtful that any goaltender, even Dominik Hasek at his absolute peak, would have been able to drag the Panthers teams of the early millennium into the playoffs. Theodore's Canadiens were bad, but Luongo's Panthers were horrible. From 2001 - 2004, the Panthers never scored more than 200 goals in a season, and in Luongo's last four seasons there they ranked 29th, 30th, 30th, and 29th in the league in shots allowed. With little offensive support and facing a barrage of shots, Luongo needed to be almost perfect for his team to win.
To make the playoffs, the Panthers would have needed around 90-95 points. That implies that they would have to score more goals than they allowed. The problem was that they scored so few that it was almost impossible for the goaltender to keep the goals against low enough. Between 2002 and 2004, the Panthers scored 544 goals, and allowed 8439 shots. To have an even goal differential, the Panthers needed their goalies to collectively save 93.6% of the shots, which is just below Dominik Hasek's all-time save percentage record of .937. Taking into account the minutes played by his backups, Roberto Luongo would have needed to play better than any goalie ever has in the history of the league, and even that would probably have left Florida with around 80-85 points, not enough for a playoff spot.
The only season in which Luongo realistically had even an outside chance to make the playoffs was last year. The Panthers had an improved offence, scoring 240 goals (21st in the league). They still were among the worst in the league in shots against, but if Luongo had repeated his dazzling play from 2003-04 the Panthers would have at least been in the playoff hunt. Unfortunately Luongo, maybe distracted by contract negotiations, had the worst year of his career (and still had a .914 save percentage and 35 wins on a poor team, which just shows the level of his talent).
So if Luongo never made it with the Panthers, why was he in the playoffs this season with Vancouver? The Canucks were almost as offensively inept as the recent Panthers teams, ranking 22nd in the league in goals for. However, they were above average in terms of shot prevention (and probably shot quality allowed), ranking 14th in the league. Facing fewer shots dropped Luongo's GAA by about half a goal from where it usually was in Florida, and despite Vancouver's punchless offence Luongo's play was enough to push the Canucks over the edge and into the postseason.
The worst teams in the league will miss the playoffs almost regardless of how well their goalies play. They don't score many goals and give up too many difficult shots, so that even outstanding goaltenders won't be able to save enough pucks to keep them in the game most nights. Roberto Luongo had virtually no chance to make the playoffs in Florida. Unfortunately there are many fans and observers that hold his lack of playoff participation against him (and there are some that still do). The absurd result of that is that many people have viewed this season as a breakout year for the man who may have been the best goalie in the NHL since 2002-03.