Cole Hamels is already on his way to another great season. Hamels’ performance is especially noteworthy since he’ll be a free-agent at the end of the season. While the Philadelphia Phillies have shown interest in locking up the 28-year-old lefty, talks with Hamels haven’t progressed much. If Hamels does reach free-agency, he — along with Zack Greinke — will be the most sought-after starting pitcher on the market. Based on their similarities, it wouldn’t be surprising for both players to receive similar offers.

We’ve already determined that based on Greinke’s career numbers, he will probably make somewhere between $140 million to $160 million on the open market. While there’s been talk that Hamels deserves the same amount of money — if not more — than Greinke, it’s unclear whether Hamels deserves to make that much. Hamels has performed well over his career, but he hasn’t been in the same class as Greinke.

When we sort all pitchers between ages 22 to 27, Hamels comes close to matching Greinke — but he comes up just short. During that period, Greinke’s 25.9 WAR just edges Hamels’ 23 WAR. Both pitchers have gotten off to strong starts this year, but Greinke already holds a bit of a WAR edge. So, unless Hamels really ups his game, he’s not likely to surpass Greinke’s WAR total by the time they both hit free-agency.

The problem with accurately valuing Hamels on the free-agent market is that many of the players who have produced similar value haven’t reached free-agency. The pitchers closest to Hamels in value all signed extensions with their teams. While Roy Halladay, Jon Lester, Jake Peavy and Carlos Zambrano are all comparable pitchers, it’s tough to compare their extensions to what Hamels will make on the free-agent market.

Barry Zito is one of the few players that we can compare to Hamels. Both pitchers produced similar value through the same points in their career, both are lefties, and both reached free-agency at 28 years old. Though Zito was already in decline by the time he became a free-agent, he still managed to get a seven-year, $126 million contract from the San Francisco Giants.

But there’s actually a good chance Hamels will make more than that. Hamels has already produced slightly more value than Zito at this point in their careers. And since Hamels just entered his age-28 season, he should widen the gap this year. On top of that, Zito signed his deal six seasons ago. Since the market has changed, Hamels can expect to make more now.

And while it’s somewhat foolish to compare extensions to free-agent deals, Matt Cain’s recent extension with the Giants helps us determine what Hamels might make. Cain just signed a six-year, $127.5 million extension. This gives us an idea of how much the market has changed since Zito signed his deal. Cain was able to make more money even though only one team was bidding on him. And for the purpose of this article, it’s extremely convenient that the same team signed both players.

Since multiple teams will be bidding on Hamels, there’s a good chance he’ll make more than Cain. But he still hasn’t been as good as Greinke. Still, the difference between the two is marginal, and it wouldn’t be surprising if both players made a similar amount of money on the market. It will be up to each team to decide which pitcher deserves the bigger contract once Greinke and Hamels hit free-agency.