Is Justin Upton a top-10 player?

Had lunch with Eric Karabell yesterday and we talked some baseball. Shocking, I know. So we got around to Justin Upton. Eric loves Upton; loves that he just turned 25 in August, that he was an MVP candidate in 2011, that he played through a thumb injury in 2012, but still ended up with decent numbers. He believes Upton is still young enough to get better, and even if he doesn't that replicating his 2011 season makes him one of the most valuable players in baseball.

Eric called him a top-10 building block and compared him to Ryan Braun. OK, I think he capitulated a little on that statement when I threatened to attack him with a plastic fork. Let's do a quick comparison between Upton and Braun, using Baseball-Reference WAR:

2009: Braun 5.9, Upton 3.8

2010: Braun 5.5, Upton 1.4

2011: Braun 7.7, Upton 5.7

2012: Braun 6.8, Upton 2.1

Their value margin is a little less extreme on FanGraphs, as Braun has 24.7 WAR over the past four seasons while Upton is at 16.7.

Of course, Braun is four years older than Upton, thus Eric's faith that Upton is still young enough to raise his game to a Braun-like offensive level.

I'm not quite as optimistic. Sure, we know young players generally improve, but Upton already has more than 3,000 plate appearances in the major leagues, since he debuted at such a young age. Upton has cut down on his strikeouts the past two seasons, but otherwise hasn't really improved, showing no spikes in his power or walk rate. If you look at star players who reach the majors at a very young age, a lot of them do hit their peak ability by the time they're 23 or 24 -- examples include Ken Griffey Jr., Alex Rodriguez, Mickey Mantle and Eddie Mathews. Now, those are all-time greats. Justin's older brother is another example: B.J.'s best offensive season came when he was 22.

My argument is that I don't believe Justin will get better; I think he is what he is at this point, 2012's thumb injury complicating the analysis a bit. Now, that doesn't mean he can't be a terrific player. He certainly was in 2011 when he hit .289/.369/.529 with 31 home runs and solid defense in right field. Does that make him a top-10 building block? I'm not so sure. His home/road splits in his career are significant -- .307 average and .937 OPS at home, .250 and .731 on the road -- and even accounting for 20-plus road games a year in San Diego, San Francisco and Los Angeles, you can't ignore a split that extreme.

Putting aside contracts, are there 10 players you'd build a team around ahead of Upton? I'd certainly take Braun, Mike Trout, Bryce Harper, Miguel Cabrera, Buster Posey, Andrew McCutchen and maybe Jason Heyward, plus there's the group of late-20s guys like Robinson Cano, Matt Kemp, David Wright, Troy Tulowitzki and Prince Fielder. I guess Upton is on that top-10 cusp if you don't include pitchers. Which makes you wonder why the Diamondbacks are shopping Upton, especially since he'll be making less than Shane Victorino over the next three seasons.

What do you think? Is Upton one of the 10 guys you'd want to build a team around? Are there too many red flags in his game to rate him one of the top-10 players?