Larry Walker will not make the Hall of Fame this year. Nor will he be enshrined anytime soon. The reasons for this are simple: (1) he had a relatively short career (17 seasons, only 12 of which he had over 400 plate appearances), (2) he played the prime of his career in Colorado, and... (3) he played the prime of his career in Colorado.
As for #1 : While career longevity is important in determining the quality of a ballplayer, it also creates contradictory arguments. To stay in the game for 18-22 seasons, a ballplayer must be good, obviously. But a ballplayer must also be lucky in health (and in some cases, major wars). A long career is what allows players to accumulate the counting stats that most voters and fans value so much when deciphering the greatness of a given ballplayer...3,000 hits; 500 home runs; 300 wins; etc. These are all great numbers. I will never argue against a member of the 3,000 hit club or 300 win club from entering the Hall. However, good health, reputation, and salary play a huge role in allowing a player the opportunity to reach these milestones.* Larry Walker was an injury-prone player, as his only 12 full seasons show. While unfortunate, his poor health does not take away from his greatness when on the field. During those 12 seasons he was among the best of all-time, and certainly one of the most dominant of his era.
*the 3,000 hit club is the most precarious, even with the steroid taint on hitting 500 home runs. A player can accumulate hits over a career without being a dominant, or even great player. If 2,500 of those hits are singles, the feat is not overwhelmingly impressive.
As for #2 : Colorado, at least until recently, was a wasteland for publicity. While Larry Walker was tearing up the NL West, not many people in the East were even paying attention.
As for #3 : That thin air in pre-humidor Coors Field. This fact should not be discounted. Walker's numbers should be viewed in context. He hit .381/.562/.710 at Coors Field, mind-boggling numbers. Away from Coors, not nearly as good, but still among the league's best, especially considering most hitters (even great ones) perform better at home than on the road. Players like Stan Musial are few and far between. In hindsight, it is unfortunate that Walker played his prime years in Colorado as this is now the strongest argument against his enshrinement. His career suggests that he would have been a dominant player in any ballpark, certainly with less superhuman-like numbers, but a dominate player nonetheless.
MON : Ages 22-27 : .281/.357/.483
COL : Ages 28-36 : .334/.426/.618
STL : Ages 37-38 : .286/.387/.520
In the strike shortened season of 1994, his last in Montreal, Walker put up a .322/.394/.587 line, belting 44 doubles and 19 home runs in 103 games. With injuries plaguing the next two seasons, Walker's peak had to wait until age 30. And his peak was remarkable. While a player's home ballpark should be taken into account, especially in borderline cases, Larry Walker is not borderline. In addition to his tremendous hitting, he was a stellar outfielder, winning seven gold gloves and owning one of the most feared throwing arms in baseball, he stole bases and ran them well, was considered a great teammate, and at times sported some stellar facial hair. To help alleviate your concerns over the pre-humidor Coors Field effect, Larry Walker's career OPS+, which takes into account park effects and league comparisons, is 140. That is 5th highest among right fielders all-time. He ranks higher than Reggie Jackson, Al Kaline, Tony Gwynn, Al Simmons, Roberto Clemente, and Dave Winfield. They are all in the Hall of Fame, and those are just the right fielders. The list of Hall of Fame left fielders and center fielders behind Walker is much much longer.
So we can't punish Larry Walker for playing in Colorado. Somebody had to. If we keep Walker out, does that mean we have to keep Todd Helton out as well? That doesn't sit well with this baseball fan.