Alexander has been a prospect in the UFC's light heavyweight division for quite some time, but had not yet beat an upper-echelon fighter.
At UFC 133, Gustafsson was granted a chance to prove himself against one of the division's unofficial gatekeepers, Hamill, and the Swede cashed in on it—big time.
Gustafsson took his time feeling out his opponent and getting his rhythm, which led to a pretty uneventful first round. But taking that time payed dividends for the young Swede.
In the second round, Gustafsson buckled Hamill standing and followed him to the ground, showing excellent killer instinct.
He eventually mounted Hamill and finished the fight with punches and elbows.
Beating Hamill is an impressive feat on its own, but the manner in which Alexander earned the victory is particularly noteworthy.
Hamill fought Quinton Jackson, perhaps the most feared boxer in the light heavyweight division and definitely a top contender, earlier this year and Jackson was unable to finish him.
The only fighter to ever finish Hamill before Gustafsson was Rich Franklin, and Franklin finished the fight with a body kick to the liver, which is a strike that is nearly impossible to come back from.
Alexander is the first fighter Hamill has ever lost to who was not a top contender (except Michael Bisping, but that was just garbage judging).
So, does this mean that Alexander Gustafsson is ready for a top contender?
I'm saying yes.
Alexander has a unique style that is tricky for opponents to prepare for and the top of the light heavyweight division could definitely use some more young talent.
Gustafsson maybe shouldn't get a top five opponent yet, but a top 10 fighter is definitely in order.
Ryan Bader, Forrest Griffin, or a rematch with Phil Davis would all make sense for the Swede's next fight.
Regardless of who he fights next, it's clear that Alexander Gustafsson is one of the most promising fighters in the light heavyweight division.