Anybody who wants to make the baserunning argument should consider how much Taveras is really adding on the bases.
We can get there pretty quickly with rough math. Run expectancy tables and linear weights tell us that the break-even point around 75% and that the average SB is worth ~.2 runs
So the formula is just
For Tavares in 2008, it comes out to 9.4 runs.
The more sophisticated version, BP's Equivilent SB Runs (EQSBR), puts it at 8.95 runs for 2008. It puts his total contribution on the bases at 11.9 runs, #2 in MLB and a pretty hefty total.
What's scary is that given the rest of his game, that baserunning production basically represents the sum total of his production above replacement. If he puts together another 2008 on the bases, he's worth about a win. If he produces another 2007, where he produced 1.4 runs on the bases, he's worth basically his major league minimum salary.
When you already have a guy who is quite likely to be at least a 1 win player for the minimum at that position in Chris Dickerson and has reasonable upside, it simply makes no sense to go out and spend a few million bucks on a guy who has a ceiling that projects no better and who has a very, very low floor.
After the Patterson debacle last year, frankly it would be laughable to spend a few million on Taveras this year. Albert Einstein would call it insane