Since he already holds a major title (the WBA's trinket), you could argue that Gennady Golovkin (20-0, 17 KO) is not a prospect anymore. And yes, I think he's already a top contender at 160, but that's more the lack of strong veteran depth in the division than anything. Make no mistake -- Golovkin is still a prospect in most respects. And he's a damn good one. That Kazakh fighter is currently without a full-time promoter, but isn't letting that stop him from fighting, either. He grew tired of Universum's nonsense and split with the firm, which was made official earlier this year. He's a 5'10" righty, former amateur star, and 29 years old.
Golovkin can fight. Ain't no joke. He can fight. If you don't take me seriously (and I can't blame you), maybe some accounts of his sparring escapades will help:
"Alfredo Angulo is a very strong, very competitive, prideful guy who has a great team behind him, but Golovkin is on another level," said [trainer Sam] Garcia, who says he watched three sparring sessions between the two over the course of one week. "His strength, his demeanor, his skill, everything he did in there was just too much for Angulo, which surprised the hell out of me."
[From Doug Fischer's notes] "His right hand is like a laser beam. It reminds me of Kostya Tszyu’s right. The way he holds his hands also reminds me of Tszyu. Come to think of it, Golovkin kind of looks of like Tszyu. He’s got the same muscle tone, Central Asian facial features and oil-black hair (sans the pigtail)."
As an amateur, Golovkin took silver at the 2004 Olympics, losing to Russia's Gaydarbek Gaydarbekov in the gold medal match. To get there, he beat eventual bronze medalist Andre Dirrell. He also won the gold at the 2003 World Championships in Bangkok, beating some very stiff competition, in this order: Matt Korobov, Andy Lee, Lucian Bute (KO-4), Yordanis Despaigne, and Oleg Mashkin. All but Mashkin have found at least some success as professionals. Golovkin is a good, strong all-around fighter with no glaring weaknesses, and any concern that he had "just a European style" have probably been thwarted by his famous sparring sessions with Angulo, Julio Cesar Chavez Jr, and now "Canelo" Alvarez.
The only con really is that he hasn't faced stiff competition professionally. He won the interim WBA title against a weak opponent, then claimed the full title against a weak opponent. It clearly hasn't been his preference, as he split from Universum in part because of their general insistence on avoiding tough fights for their clients. He's been dying to get a fight with Hassan N'dam N'jikam, but it hasn't happened. At 5'10", he's on the short end of middleweights, but he makes up for that by being good.
Other Middleweight Prospects
The aforementioned Hassan N'dam N'jikam (26-0, 17 KO) is another serious prospect in a division that does have a lot of them, but he got a bit of a break last time out against Giovanni Lorenzo. Fernando Guerrero (21-0, 16 KO) is a BLH favorite and TV regular who seems to have stagnated at about the level he was at in 2009, to be honest. He's a good fighter, but doesn't look like he'll ever be more than that. Maksym Bursak (22-0-1, 8 KO) is a solid prospect from Ukraine, but not a future star.
I think it would be foolish to give up on Canadian puncher David Lemieux (25-1, 24 KO) just because he lost to a veteran fighter who fought exactly the right fight. Lemieux still has real skills and a big punch, and he's got the right backing to correct his young man's flaws. Top Rank's Matt Korobov (15-0, 9 KO) hit a wall a while back and has been protected to a huge degree. He once excited observers, but is now almost a forgotten man, hidden deep on off-TV undercards. I'm not quite as "forgiving" of Daniel Jacobs (22-1, 19 KO) as I am Lemieux -- Jacobs just seems to have some serious issues that are going to be very, very hard to correct. He'd be wise to emulate Victor Ortiz, another super-hyped Golden Boy prospect who lost to a relative unknown it turned out could really fight. Ortiz has recovered. Jacobs does have the skill, but does he have that will?
The good news for Julio Cesar Chavez Jr (42-0-1, 30 KO) is that he'll make a lot of money no matter what. Andy Lee (26-1, 19 KO) is kind of in the same boat -- he's got the Irish thing in his favor, plus he makes for exciting fights.