Cliff Lee would make the St. Louis Cardinals better in 2013. (I like to lead with my most controversial point; let me know if you hear about any sports-talk radio openings.) He'd make the Cardinals better in 2014 and 2015, too, though he'd also make them $25 million more expensive.
But given the price—Carlos Martinez et al, if you don't mind pushing two rumors together for a day or two and speculating on which of the top prospects the Phillies would inevitably demand—the much-more-important thing is how and to what end he makes the Cardinals better.
The Cardinals' top prospects offer a reasonable chance at a significantly better team over the next several years. Oscar Taveras might eventually provide as many wins (and much more cheaply) as Cliff Lee; Kolten Wong might find an alternate universe where Matt Carpenter is not already living out the 90th-percentile Kolten Wong projection; even guys like Greg Garcia, in bulk, are insurance against a Pete-Kozma-style black hole on any one side of the ball.
A few of the Cardinals' prospects will, if things break right and depending on your WAR valuation, eventually outperform two-and-a-half $25 million seasons of Cliff Lee. Shelby Miller is pretty close right now [results not typical].
Which is all just to say that the wins Cliff Lee will produce after this season are important, but only because they raise the stakes of the whole transaction—they leave their collective thumb on the table while the Hypothetical Cardinals and the Hypothetical Phillies are making a much purer deal about trading tomorrow's wins at a discount for one or two today. Cliff Lee offers an excellent chance at a better team over the next year, and a reasonable chance at a team that is significantly, playoff-rules-significantly, better.
That win probably won't keep the Cardinals in or out of the postseason, but the new wild card rules make spare wins like it much more valuable. So I don't know that I'd agree with trading a top-flight prospect or two for Cliff Lee, but I can see the appeal.
What I can't see is the Cardinals seeing the appeal. Because what we've seen so far this year just doesn't suggest a team that's concerned with squeezing every last win from the regular season. This is a team, most obviously, that's carrying three catchers—ostensibly because it allows them to play Yadier Molina more (and maximize their regular-season wins that way), although I'm not sure the infinitesimal chance of blundering your way into emergency catcher territory for a couple of innings justifies the caution.
It's also a team that has kept two of its best, most ready, most tradable prospects in the minor leagues despite the difference they could probably make at the major league level. This is not just the moment in a successful season in which teams trade their major-league-ready pitching prospects—it's the moment in which some of them play those prospects.
Tyler Lyons' numbers are great, and I like John Gast Pickoff Watch more than most. But compared to the back of the rotation as it's currently constituted, Michael Wacha and Carlos Martinez offer a chance—just this side of reasonable, I think—of making their team better this year. And then next year they're still Michael Wacha and Carlos Martinez. If the Cardinals are so nervous about the future that a couple of wins are worth trading them, it seems strange that they haven't behaved as though a chance at those same wins are worth rushing them.