The list of upcoming free agent position players is what’s politely referred to asĀ interesting. With an increasing number of players signing long-term extensions before they ever meet free agency (and looking at the recent Troy Tulowitzki, Ryan Braun, and Joey Votto contracts, why not?), the pickings are increasingly slim, and it looks like it is going to be that way for a while.

Obviously, Josh Hamilton and David Ortiz are two big names on the list, but neither is an obvious high-demand guy like (to stick with just a few examples), say Prince Fielder last year, Carl Crawford the year before (yeah, he really was in demand back then), or Mark Teixeira in the 2008-2009 off-season.

Hamilton is obviously immensely talented. However, leaving aside his “personal problems,” he still has several factors counting against him:

  • He’s going to be 32 next year;
  • 2012 marks the first time since 2008 in which he has played at least 140 games; and
  • His lack of plate discipline is such that if he loses bat speed, things could get ugly pretty quickly.

Ortiz is an awesome hitter, having somehow cut his strikeout rate to career-lows in his late 30s while keeping all of his power. However, he, too, is not without chinks in his armor:

  • He’s in his late 30s;
  • He’s still a big guy despite seemingly being a bit more trim than a few years back;
  • Injuries have limited him to less than 100 games this season; and
  • At this point, he should be strictly limited to designated hitting duties — which makes him more difficult to work around, roster-wise, with interleague play going on all the time starting next year.

That is not to say there is not value in the free agent market. I am simply saying there are no obvious players that every team will covet. I do think Marco Scutaro can provide good value, but it really isn’t that exciting to wonder if some team will get him for just $2 million.

If there is one player who is reaching free agency, has obvious physical talents, is young enough that he is not on the steep end of the decline curve, and might even have some upside left, it is B.J. Upton. The Rays center fielder has long been a subject of trade speculation, and after a rough start to the season, he is at the center of more welcome attention with a late season power surge: 17 home runs since the beginning of August, and 10 in September as the Rays try to make another miracle push to the playoffs.

There are two issues with Upton that are important, but are (relatively speaking) going to get the short shrift in this post: his health and his fielding.

Upton did miss a couple of weeks this season with back soreness, and had shoulder surgery in the 2008-2009 off-season. Generally, though, he’s been durable, getting in at least 600 plate appearances and playing more than more than 140 games every year since 2008 (well, he’s at 139 games so far this year). I am not doctor or trainer, so I am not going to into realms I cannot speak to, but generally, Upton has a good health record.

As far as his fielding, well, we know that we really do not know much about measuring fielding relative to what we know about measuring offense. As a prospect, B.J. Upton was a shortstop, but a bad one, and that probably kept him from getting to the majors faster. In 2007, the Rays tried him at second base (where he looked pretty bad) before moving him to center field, where he looked much better. Upton is a fast guy with a strong arm, which is affirmed by the generally positive evaluations his fielding gets on the Fans Scouting Report.

Fielding metrics are all over the place, though. For his career, UZR sees Upton as about 20 runs above average over about 7000 innings – approximately five seasons. On the other hand, Dewan’s Defensive Runs Saved has him at at 34 runs below average. Without getting into the technical differences between all the metrics, Baseball Prospectus‘ FRAA has Upton as practically average in center field. I personally (subjectively) feel like he’s pretty good out there, but when in doubt — assume average (regression!).

With those not-as-brief-as-I-thought-they-would-be qualifications in mind, the real mystery with Upton lays in his bat. Yes, it could be argued that Upton hasn’t strayed far from his average of about four fWAR a season since he became a full-time player, and looks headed for something like that now. Moreover, a look at his offense the last three seasons reveals: 113 wRC+ in 2010, 115 wRC+ in 2011, and 111 wRC+ so far in 2012. His career wRC+ is 110.

But part of what makes Upton puzzling is that he has done things in different ways. Way back in 2007, he had both power (.209 ISO) and a high BABIP (.393). The next year his BABIP was still pretty high (.344) but his power went down (.128), perhaps in part due to recovery from shoulder surgery. Since then, however, his BABIP has been pretty unremarkabale either way: .310, , 304, ,298, .297. Upton’s power rebounded somewhat in 2010 (.187 ISO) and 2011 (.186), but this year has seen a seeming return to 2007 for Upton, with a .204 ISO on 26 home runs. What is particularly enticing is that, as mentioned before, Upton has hit 17 of those in the last two months. Does this mark a new level of true talent for Upton?

Let’s leave aside the problematic notion of a breakout and just look at other evidence. Upton is indeed hitting home runs on contacted balls in play at the highest rate (6.6 percent) he has since 2007 (7.4 percent), and it has been increasing each year since going down in 2008. This is not to put emphasis on a “trend” but simply to note that, yes, Upton’s home run rate has increased. That is not totally unexpected for a player in his mid-20s.

Let’s look at other evidence of Upton’s “newfound power.” According to ESPN’s Hit Tracker, in 2012, B.J. Upton’s home runs average 397 feet in standard distance (that is, normalized for comparison), and 103.9 miles per hour off of the bat. In 2011, those numbers were 394 and 104.5, respectively. In 2010, they were 104.1 and 396.4. In other words, at least in balls that went out of the park, he’s hitting them pretty much as hard as he was the two previous seasons.

While there has been an increase in power, it has been offset by his plate discipline getting worse. Upton has always struck out a lot, but in 2008, 2010, and 2011, that was somewhat offset by him walking at a good clip. However, this season, he is walking in only seven percent of plate appearances. While Upton has always had below-average contact stats, this year has seen a significant drop in those numbers, while he is also swinging more at balls both inside and outside of the zone. To make matters weirder, Jeff Sullivan points out that Upton’s power surge the last couple of months also corresponds with his plate discipline breaking down.

This is not to say that Upton has actually gotten worse. Power is power, and while it is not the only tool necessary for success at the plate, it is a nice one to have. However, in Upton’s case, while there has been a slight uptick this year (as a whole) as compared to previous seasons in home run rate, it is not far from what would be expected (unless one cherry-picks the last two months and ignores the prior part of 2012 — a bad practice all around). The balls are being hit about as hard as in previous years, but whatever gains that Upton has in that area are offset by a dramatically lowered walk rate.

Does this mean that it is impossible for Upton to maintain this level of power next year while bringing up his walks? Of course not. And, in fact, given his age, even if he just keeps doing the same thing he has the last couple of years, he is still a very valuable free agent — there are not many four win players in their 20s two make it to free agency any more. But uncertainty aside, I do not think there are compelling reasons to think he has suddenly become more than that during the last two months.