Mike Leake is a perfectly competent Major League starter. Over each of the last three seasons, he was slightly above average at run prevention and slightly below average with peripheral stats--he exhibits good control but averages 6.06 strikeouts per 9 for his career, a mediocre rate given the soaring strikeout rates of the modern era.
There is absolutely value in being a league-average pitcher, particularly one with a track record of being able to pitch a ton of innings. Leake is both of these. And with the loss of Lance Lynn for 2016 after off-season Tommy John surgery, and with the St. Louis Cardinals entering 2016 with four good-when-healthy starting pitchers who have each had durability issues, having somebody to eat innings throughout the season in the Lynn mold is a definite plus. In a vacuum, the Cardinals are a better baseball team with Mike Leake than without him.
But it's hard to not look at the Cardinals' acquisition of Mike Leake today, with a reported contract length of five years for $80 million with a mutual option for a sixth year, as an overpay.
It's not necessarily a huge overpay in the traditional sense: Leake is relatively young for a free agent (he just turned 28 last month) and although his statistics are somewhat pedestrian, Fangraphs estimates he was worth $15.4 million per season over the last two years by free agent standards. Adjusted for inflation and the growth of Major League Baseball, the $16 million per year price tag is fair. Even an average pitcher can command this kind of contract because of what value he represents over the so-called "replacement level" player as conveyed in "wins above replacement".
But in the case of the Cardinals, Leake is probably not replacing a "replacement level" pitcher. The odd man out with the addition of Mike Leake is Tyler Lyons, who has been worth 0.9 fWAR in 149 2/3 career innings. The Steamer projection system has Lyons as a 1.2 WAR pitcher in 85 innings for 2016. And while that may be a tad optimistic (and perhaps influenced on a rate basis by his projected role in the bullpen, where virtually all pitchers give up runs at a lower rate), it does reflect a widely held belief that Lyons could be a solid starter, if not necessarily an ace.
The presence of recently-injured starters Adam Wainwright, Jaime Garcia, Carlos Martinez, and Michael Wacha made rotation depth a concern; Lyons all of a sudden would need to transcend the "fifth starter" archetype if one of the guys ahead of him were to go down with an injury. But the team also has Marco Gonzales and Tim Cooney, both of whom are projected to be above replacement level.
David Price, whom the Cardinals pursued, would have represented an obvious improvement for the team: he immediately would have been the team's ace. He would have cost the GDP of Greater St. Louis (note: this is probably hyperbole. Probably) but he would have solidified a rotation in which the team's worst starter would still be projected as above league average. It would be unfair to look at Price's surplus win production as simply his WAR total, since Tyler Lyons is still better than the scrap-heap journeyman or unproven minor leaguer synonymous with replacement level classification, but Price would represent a clear improvement over Lyons because he's just that good of a pitcher.
Even if we said Lyons as a starter is below average, at 1 WAR, Steamer has Mike Leake worth 2 WAR. He creates a one-win improvement for $16 million. And despite the escalating cost of a win in baseball, we aren't quite to that level.
On the bright side, this isn't the kind of contract one would expect to be terrible at the end. Leake will be 32 at the end of the contract, and although arm trouble is a concern with any pitcher, there's not much reason beyond sheer blind fatalism to expect Leake is more likely than anyone else to experience it. Maybe the Cardinals expect to work the old Dave Duncan magic to give new life to a pitch-to-contact pitcher (just without Dave Duncan, not a small part of the equation). But the trick was far more impressive when it was being done for low-cost options such as Jeff Suppan. At $16 million per season, for what to this point has amounted to a #4 starter, this move just doesn't have the same upside, and may not actually represent eighty million dollars worth of improvement over the next five seasons for the Cardinals.