Winning Pitcher--Hawkins???

[TriggerMN]

Today's Twins-Yankees game. Twins lead after 4 innings,
1-0. Santana comes out with an injury, not able to go the 5 standard innings for the win. The first pitcher out of the pen is Rick Reed, who becomes the pitcher of record and pitches 2/3 inning, followed by J.C. Romero pitching 1 1/3, LaTroy Hawkins pitching 2, and Eddie Guardado pitching 1. The game was never tied, yet Hawkins got the win. Huh?

Is this one of those "scorer's discretion" rules, where the official scorer can give the win to whomever he feels deserves it most? Can anybody supply a rule for this?

Also, if this is indeed the case, can the scorer still give the win to the starting pitcher if he feels that the starting pitcher deserves it by being the best pitcher, or is the 5 innings a steadfast rule?