It is one of the toughest things that coaches have to deal with. You lose a star player on your team. Not just any star but your QB in football or your goalie in hockey. It places a tremendous amount of pressure on the whole franchise.
I feel that in hockey if you lose your goalie early in the season you can recover from the amount of games you will play. The NHL season is now 82 regular games. In the NFL you only have 16 regular season games. I would think it would be tougher in football to replace your QB.
In the case of the Patriots they have lost not only the face of their team but the face of the league. This is going to put a lot of pressure on the rest of the team. Everyone is going to have to pick up the pace a little bit more. I also think relying on one player makes for trouble down the road like now for the Pats. Everyone looked to Brady to be the leader of the team and now he is out of the mix. Cassel the back up who has not started a game since high school is in a tough spot. He can either step up or fall down. It is all up to him.
In hockey if you are lose your goalie you have time to recover if it is early in the season. However if you lose your goalie late in the season it could have a very bad effect on the team. If you are headed to the playoffs in hockey and lose your top goalie and your backup has not played much in the regular season you could have problems. On the other hand sometimes goalies can get hot and lead a team to victory. It happens only once in a while but not as much as coaches and fans would like.
In summing up I would say this can have an effect on teams in both sports but I would think it is worse for football. Less games and more room for mistakes. In hockey you have a goalie go down and still have 40 games to play and build from that. The only place to really decide if it tough is play the games and see what happens