Martin Brodeur is a one-of-a-kind goalie. As the all-time leader in wins, shutouts, minutes, wins in a season and many, many other records, he's shown that he is capable of things no one else is.
He's been the Devils' starter since 1993-94 and he's started most of almost every season since then. This is important, because the Devils have built themselves completely around their goalie.
Brodeur moves the puck like few goaltenders have ever been able to: His passes are spot-on all the way into the attacking zone and his stick-handling is a factor that drastically alters a game's flow. He makes every dump-in a possibility for a counter-attack.
Hedberg has admirably been trying to fill in, and sometimes he pulls it off. More often, though, his passes are off-target—sometimes to the opponent—and his attempts to handle behind the net end in disaster more than occasionally. It's not a knock against him, it's a testament to how special Brodeur is.
And that's just it. Brodeur can't be replaced.
When every skater on the Devils is used to playing in a system partially based around a puck-moving, versatile goaltender, they can't succeed in the long term with a guy like Hedberg.
The team's identity and play is based around its goalie. If it wants to make a late-season push or a playoff run, it needs No. 30 tending the goal.