Due to health issues, Canada missed Mario Lemieux (on rehabilitation for his back injury), Cam Neely (leg injury), Patrick Roy (sinus operation in August) and Joe Nieuwendyk (hurt his left knee during training). Others were healthy, but turned down Hockey Canada's invitation nevertheless: Ray Bourque (he prefered his summer break), Mark Recchi (free agent, didn't want to cover his own insurance), John Cullen (same as Recchi). And then there are those wo were cut from Mike Keenan's roster, guys like Joe Sakic, Adam Oates and Brian Bellows. Last but not least there's the odd case of Steve Yzerman who was actually on the roster, but saw no ice time in the first two games and was cut from the roster after game 2. The reason? Ask Mike Keenan.
The USA also had its absentees due to the insurance issue. Just like Recchi and Cullen, Kevin Stevens and Phil Housley were unwilling to cover their insurance and missed the tournament. On the other hand, several players on the US roster paid for their own insurance. So did Eric Lindros, whose appearance in the tournament made headlines, albeit for a different reason: 18 years of age, no experience outside of junior hockey, but the "Next One" was considered ready for Team Canada.
Despite missing Stevens and Housley, they USA had a good tournament. With Chelios and Leetch on defense, with young forwards like Mike Modano and Jeremy Roenick stepping in and with the inclusion of Brett Hull, they finished second only to Canada, a massive improvement over their earlier Canada Cup performances.
In contrast, the Soviet Union had a devastating tournament. With the change of generations, heroes like Krutov, Larionov, Makarov, Khomutov, Bykov and Fetisov all were gone. Of the younger guys, Kamensky was injured, Bure was left out because he refused to sign a new contract with CSKA Moscow and Mogilny was a persona non grata for defecting in 1989. In addition, the Soviets lost their best goaltender, Arturs Irbe, to the newly emerging republic of Latvia. Aside from a couple of veterans, Team USSR was very young: Malakhov was 22, Fyodorov 21, Butsayev 21, Kovalenko 21, Korolyov 20, Zhamnov 20, Filimonov 19, Slava Kozlov 19, Zhitnik 18...
All in all, the Soviet Union, Czechoslovakia and Sweden, three traditional powerhouses, had bad tournaments. Canada suceeded, but considering the roster issues and considering the legacy of 1976, 1984 and 1987, the 1991 CC campaign doesn't appear very glamorous. Finland had a good tournament, but not good enough to contend for the cup. The USA had a very good tournament, but far and away overshadowed by the 1996 World Cup. Thus, the 1991 Canada Cup is not the most fancy tournament to remember from pretty much everyone's point of view.