Before the baseball season started, I wrote a piece about how the Cubs were expected to be the best team in baseball. Now 70 percent through the season, they are the best team in baseball. They're the only team with a winning percentage over .600, and their run differential of +201 is 62 runs more than the second-place team, the Nationals.

So things are going to plan. The only deviation is Jason Heyward, their highest-profile free-agent signing. He signed for eight years and $184 million, and he's hitting .227/.304/.314, with the sixth-lowest wRC+ among qualified hitters. The five players with a worse wRC+ are all punchless middle infielders; Heyward looks the part of and plays the position of a slugger.

His defense is still excellent, ranked 8th best among all players by Fangraphs. His baserunning is still fine; by Fangraphs's BsR metric, he's in the top 50, despite that measure being weighted towards players who hit well (you have to get on base to run bases). So despite his disastrous offense this year, he's still a pretty good player—he's been worth 1.3 wins above replacement by Fangraphs' calculations, putting him on pace to finish at 1.8 WAR. That's how good his defense is. SABR's Defensive Index has him as the best fielder in the National League (the best overall is the White Sox's Adam Eaton, whose defense I've written about before).

I got to thinking about Heyward because of something the great baseball journalist Joe Sheehan tweeted.

Every offseason, baseball nerds try to figure out what the cost of a win is, by looking at how much teams spend on free agents and how many wins above replacement those players are expected to be worth. Last year, that was about $7.7 million, according to FiveThirtyEight's Neil Paine. Lewie Pollis of Beyond the Box Score found that it was about $7 million in 2013, a huge increase from about $4 million in 2005.

This can get complicated. Fangraphs's Dave Cameron, for instance, took an approach where he factored in both inflation and players' aging curves to look at the value of long-term deals. That gave him a 2014 value of $6 million per win.

I decided to keep things simple. On every Fangraphs player page, there's a "Value" section that gives a dollar figure for how much a player has been worth that year. For Heyward in 2016, that's $10.5 million for 1.3 WAR on the year so far, which comes out to about $8 million per win. That's close to Paine's calculation from last year, so I went with $8 million as a ballpark figure for the cost of a win in 2016.

So back to Heyward. He's been worth 1.2 WAR so far this year, according to Fangraphs' numbers. (Baseball Reference has Heyward at 1.1 WAR, Baseball Prospectus at -0.2 WAR because he fares poorly by their defensive metric, though they project him to finish with 1.0 WAR.) Based on how many games the Cubs have played, he should finish with 1.8 WAR. If that's your basis, Sheehan is overstating Heyward's performance this year. But he's basically right about what he's being paid—$184 million over eight years is $23 million per season. If a win is worth $8 million, then Heyward is being paid a bit less than a three-win free agent. He'll probably end up being about a two-win player in 2016, maybe less (he's hitting just .182 in August).

If Heyward is being paid like a three-win player, then his contract could still end up being a good long-term deal. He's just 27 and he's been a five-to-six-win player every time he's gotten at least 600 at bats, and he's been about a 4.5-win player on average. So looking just at this season isn't meant to be a judgment on the contract as a whole. It's certainly worrisome how badly Heyward has hit this year, and as Jeff Sullivan writes, it doesn't seem to just be bad luck. But I suspect few would predict that Heyward will hit this badly for the next seven-plus years. Even a diminished Heyward could be a consistent three-win player.

But this year he's not. So I was curious how he ranked compared to the rest of his free-agent class. I took the 25 biggest free-agent deals, calculated how many WAR those players are on pace to end up with, and got a dollars-per-WAR value. Then, using the $8-million-per-win figure, I calculated how much surplus value players provided for their team—or, by contrast, how much teams overpaid.

The good news? The Cubs got great value from the Lackey and Zobrist deals. The bad news? Heyward's one of the worse overpays, at least for this year. Interesting side note: the average surplus value is about $1 million. There's not too much blood to squeeze from the free-agent stone, at least cumulatively.

The above is a bit of an apples-to-oranges comparison, though; the market for different positions is different depending on teams' needs and the free-agent market. What happens when you narrow it down to outfielders, or at least players who have played a substantial amount of outfield this year?

Cleveland did awfully well with Rajai Davis (1.8 WAR last year, 1.4 in 2014), on a one-year, $5.25 million contract, from which they'll probably end up with about 3.6 WAR. By contrast, the Cubs paid $13 million for Dexter Fowler for one year; he'll probably end up at about 4 WAR. But Fowler had a better track record than Davis coming into the season. Ben Zobrist is $14 million a year, but will probably be about a win better than Davis. (Marginal cost is another factor.)

Heyward? Not great, not a disaster either. That award goes to Justin Upton, who has been worth -1.0 WAR this year—negative on both offense and defense—and is being paid $22 million a year.

How'd the Cubs do on the free agent market as a whole? Pretty well.

That averages out to $9 million in surplus value, or a bit more than one win. Overall, their offseason was a success, and while Heyward has been a disappointment at the plate, he hasn't exactly been a bust. The Cubs spent fairly big money on relatively safe bets, hitting on three of them. Heyward wasn't signed in a vacuum; the Cubs have built a deep team, and if the Heyward contract was a bit of a bomb, there's enough talent to absorb it.