Tim Lincecum has done more than enough during his career to merit a big contract. But after reportedly turning down a five-year offer worth “at least $100 million” — and instead opting for a two-year, $40.5 million extension with the San Francisco Giants — it appears Lincecum will wait to sign that huge free-agent deal. Lincecum has been one of the best starters in baseball since his debut — winning back-to-back National League Cy Young awards in his first two full seasons — and he’s definitely in line for a big payday. But given pitchers’ unpredictability, Lincecum’s decision to play the free-agent market could come back to haunt him.

During the past four seasons — when Lincecum became a full-time starter — his 24.7 WAR is good for fifth best among starting pitchers. During that same period, Lincecum is first in strikeouts, second in FIP and seventh in innings pitched. It isn’t just that Lincecum is good; he’s also been incredibly durable over his career. On top of that, he’s just 27-years-old. By the time he reaches free-agency in 2014, he’ll still be in the prime of his career. Given the rumors that Lincecum could be the game’s first $200 million pitcher, it’s hard to fault Lincecum for wanting to test the free-agent market. Still, Lincecum’s shown some signs of decline. And that could make him a far-less attractive option two years from now.

With pitchers, there’s always a risk of a severe injury, but Lincecum’s heavy workload could make him even more of a risk. While his durability might be seen as a positive, it’s also caused Lincecum to throw a whole lot of innings in the early part of his career. While a heavy workload isn’t a guarantee that a pitcher will get injured, younger pitchers are more susceptible to workload-related injuries. Outside of his rookie season, Lincecum has not been handled with kid gloves.

Tim Lincecum Games Started 110+ Pitches Thrown 120+ Pitches Thrown PAP Rank 2008 33 18 5 1st 2009 32 17 5 4th 2010 33 12 4 11th 2011 33 20 4 4th

Lincecum has ranked in the top five in pitcher abuse points in all but one season since 2008. In his first full season as a starter, Lincecum ranked first in the category, throwing at least 110 pitches in more than half of his starts. While he’s managed to stay healthy despite his heavy workload, the effects of being abused so young have shown up in other areas.

In 2008, Lincecum’s average fastball was 94 mph, which tied for the sixth-hardest fastball among major league starters. After two seasons of heavy work, things bottomed out for Lincecum in 2010, when his average fastball velocity came in at just 91.2 mph. Though Lincecum regained some of that velocity in 2011, his fastball actually rated negatively, according to pitch values. That’s the first time that’s happened over Lincecum’s career. Lincecum has compensated for the velocity loss by developing one of the most devastating change-ups in the league. While that’s become his new go-to pitch, it’s unclear whether Lincecum will ever regain his 94 mph gas.

Lincecum has also seen some decline in his stats recently.

Tim Lincecum K% BB% FIP FIP- xFIP xFIP- WAR 2008 28.6% 9.1% 2.62 60 3.13 72 7.5 2009 28.8% 7.5% 2.34 56 2.83 66 8.0 2010 25.8% 8.5% 3.15 81 3.09 77 4.9 2011 24.4% 9.6% 3.17 84 3.36 87 4.4

After peaking between 2008 and 2009, Lincecum has experienced decline in some crucial areas. Last season, his strikeout rate fell to 24.4% — his worst showing since his rookie season. Lincecum also walked more batters than usual last season, leading to the second-highest walk rate of his career. After posting 15.5 WAR between 2008 and 2009, Lincecum has been worth 9.3 WAR during the past two seasons.

That’s not to imply at all that Lincecum is a bad pitcher. Most pitchers would kill to post Lincecum’s stat line from last year. If he has declined, it’s been from exceptional to very good. As his FIP- shows, he’s still much better than the average National League starter.

But there’s still that nagging trend. Even if Lincecum’s true talent is 4 to 5 WAR per season, as opposed to 7 to 8 WAR per season, that’ll still be enough to land him a huge contract once he hits free-agent market. But if his peripherals continue to decline — or he gets injured — he could regret not taking a long term deal right now.

Unless you believe Lincecum will get better, which would be tough to do with his current performance level, there’s little reason to believe his value will be any higher than it is right now. There’s always a chance he’ll get a better offer on the free-agent market, but considering there are already some warning signs, he’s definitely taking a risk by turning down the Giants’ long-term offer now.