Who produces runs? One of the largest differences of opinions between people within the game and analysts outside of it concerns the utility of the RBI in describing a player’s value. Some announcers and players (and arbitrators) treat it as a hallmark of quality, while statheads of no lesser stature than Bill James have called it little more than a statistical footnote.

In the wake of the nonsense about how the White Sox won it all last season with speed and defense – when they really won with power hitting and power pitching – it’s worth noting that the truth about what RBIs tell us lies somewhere in between these opposing views. There’s something to be said for players who deliver on opportunities created by their teammates. A hitter’s RBI chances are created for him by two factors: where he hits in the lineup and how good his teammates are.

The big league leaders in baserunners on board when they come up won’t surprise you: Boston’s David Ortiz with 298, the Yankees’ Alex Rodriguez with 289, Atlanta’s Andruw Jones with 281, Baltimore’s Miguel Tejada with 277, Texas’s Mark Teixeira with 276, and the Mets’ David Wright with 272. Equally unsurprising, Ortiz, Jones, and Wright rank in the top six in RBI. (A-Rod and Teixeira do not, but we’ll get back to that.)

Counting RBIs doesn’t tell us how good a hitter is at driving in runs, but counting how often a hitter converts his RBI opportunities does tell us something more about whether a guy is delivering on the opportunities he’s given.

That’s why Baseball Prospectus tracks RBI opportunities on our site, to get a sense of who’s really coming through. Instead of tallying RBIs or counting the number of baserunners – both of which really tell us who’s batting in the heart of the order – it makes sense to see who’s excelling at driving in the baserunners he actually gets.

So who’s doing the best at driving guys in? The answer isn’t that surprising. By driving in 22.6% of the hitters he comes up with, Houston’s Lance Berkman is leading the majors in RBI despite ranking only 63rd in RBI opportunities. Albert Pujols (21.3%) ranks second among qualifying big league hitters, and the Mets’ Carlos Beltran fifth (20.2%).

But hidden in between those three superstars are some less obvious names: Arizona catcher Johnny Estrada (20.9%) and Texas outfielder Gary Matthews Jr. (20.5%), neither of whom will appear on any MVP ballots in October. Seeing their names in the middle of a league leaderboard might make you question how useful the information is, but there’s no value judgment here: these guys have done well with the opportunities they’ve been given. But will they do it over a full season? That’s where we get into the more difficult question of whether hitting with runners on base is a skill or not.The leaderboard for 2005 might encourage you to think that it is: the top three hitters in converting baserunners into runs were Teixeira (20.2%), Manny Ramirez (19.7%), and Ortiz (19.3%).

But it’s really not that simple. Consider last season’s leader, Teixeira. He has power to all fields in a park that smiles on power, and after hitting .281 and .301 the last two seasons, making contact isn’t a problem for the young slugger. But while he’s not doing badly in terms of making contact this year (.268), he’s only driving in 13.7% of his baserunners, and with his slugging dipping to a career low of .431, it’s hard to plate people if you’re not doing the same sort of damage powering the ball. And A-Rod? This is an area where he suffers by comparison to Ortiz for a third straight season, putting 13.8% of his baserunners on the scoreboard this season, still behind Ortiz despite Papi’s dip down to a 16.4% clip. In 2005, A-Rod drove in 15.1%, and 14.2% in 2004.

Are there any consistencies among those who aren’t great RBI guys? Consider one team’s target of choice. Reds fans have been frustrated with Adam Dunn’s seeming inability to drive in anyone but himself with any frequency. He might seem the prototype for a hitter that statistical analysts love and scouts deride: patient at the plate, long swing, tons of power, and prone to striking out. Those skills help him hit plenty of home runs and draw walks to create scoring opportunities for his teammates, but they also suggest that Dunn might not be the best guy at shortening his swing and making contact for an RBI single. Because he’s usually hitting in the middle of the order, Dunn gets plenty of opportunities to generate runs, coming up with 237 ducks on the pond, just edging out Austin Kearns’s 234 mark for the team lead. Dunn has 54 RBI, Kearns 49, but Dunn has hit 26 home runs to Kearns’s 16.

Kearns is better at putting the ball in play, and by driving in 14.1% of his baserunners to Dunn’s 11.8%, it seems pretty obvious. Except that it isn’t. Dunn is doing better than teammates Felipe Lopez (9.6%), Scott Hatteberg (9.7%), Ryan Freel (7.4%), all of whom hit for contact better than he does. Kearns isn’t even the team’s best – Ken Griffey Jr. leads the team by driving in 19.7% of his baserunners.Veteran experience is no guarantee either – the next-best hitters in terms of converting baserunners to runs on the team are youngsters Brandon Phillips and Edwin Encarnacion.

So, it looks like failing to drive in 80% of the guys on base when you come up is another one of baseball’s definitions of success. From 1960 to the present, George Brett set the highest mark for a regular player by driving in 25.5% of the runners he had on base. But who’s second in that time? Bill Buckner, with the 1981 Cubs. But to be fair to Buckner, what this sort of information tells us is that we should be giving more thought to who’s done a great job with their RBI opportunities, not just who just happens to be hitting in an RBI position.

Ms. Kahrl is a writer for Baseball Prospectus.For more state-of-the-art analysis, visit www.baseballprospectus.com.