8 Upcoming Free Agents Who Have Made Themselves Irreplaceable in 2013

The 2013 free-agent class is starting to take shape and there are some big names expected to be available at the conclusion of the World Series.

Some will bolt for new clubs while their former team is left to figure out how to replace their production. However, replacing an impact player with someone who can provide equivalent value at the same position is not always possible. It's sometimes more realistic and cost-effective to make minor upgrades at several positions.

For example, the Texas Rangers lost one of the best hitters in baseball when Josh Hamilton signed a free-agent deal with the Angels this past offseason. To help supplement the loss, the Rangers signed catcher A.J. Pierzynski, designated hitter Lance Berkman and utility man Jeff Baker, and expected to see immediate production out of rookies Leonys Martin and Jurickson Profar.

While the offense hasn't been great overall and the pitching staff is the biggest reason why they're still one of the best teams in baseball, the decision to not put all their eggs in one basket by re-signing Hamilton or some other high-priced superstar has allowed Texas to better spread their talent throughout the roster.

It has also afforded the Rangers the luxury of making key midseason additions through the acquisitions of Matt Garza and Alex Rios. 

Here are eight soon-to-be free agents whose current team will have a very hard time replacing them if they sign elsewhere. These clubs might need to follow the Rangers' plan of retooling so as to not suffer a dropoff in performance in 2014.

A.J. Burnett, SP, Pittsburgh Pirates

The Pirates are one of the best teams in baseball, with young talent already on the roster and more on the way. But regardless of how many talented pitchers they have waiting to fill out their rotation, it won't be the same without a veteran workhorse like A.J. Burnett leading the way.

In 52 starts since joining the team in 2012, the 36-year-old has a 3.29 ERA with 3.0 BB/9 and 8.8 K/9. He's averaged over six innings per start with a 63 percent quality start rate (at least 6 IP, no more than 3 ER) and has pitched at least seven innings 22 times.

The veteran has also allowed just two earned runs or less in 67 percent of his starts as a Pirate, making him one of the most reliable starting pitchers in baseball over the past two seasons.

Don't get me wrong. A 2014 rotation of Francisco Liriano, Gerrit Cole, Jeff Locke, Charlie Morton and Jeanmar Gomez—with top prospect Jameson Taillon a possibility by June or July—could be great.

However, losing Burnett's stability could also have the Pirates looking for reinforcements by midseason. 

Robinson Cano, 2B, New York Yankees

The Yankees could find it impossible to replace second baseman Robinson Cano's production if he leaves as a free agent.

This is why they're probably hoping that Alex Rodriguez's 211-game suspension holds up. If it does, they can reinvest the large savings from not having to pay A-Rod to help retain Cano, who is expected to net the biggest free-agent contract of the upcoming offseason.

The 30-year-old, who has an .856 OPS during his nine-year major league career, could seek a contract in the eight-year, $200 million range.

Utilizing that amount to spread throughout the roster as an alternative wouldn't be a bad idea, but the internal options—as well as those in free agency—are so limited that the downgrade at the position would be severe. 

Regardless of how good an offseason general manager Brian Cashman could have, it's hard to see this Yankees team getting much better without Cano in the lineup.

If they have payroll limitations once again, they might not have a choice in the matter.

Shin-Soo Choo, OF, Cincinnati Reds

With the presence of top-prospect Billy Hamilton in the organization and the assumption that he'd be ready to take over as the starting center fielder in 2014, the Cincinnati Red's acquisition of Shin-Soo Choo this past offseason looked like a temporary solution.

Choo has been so good out of the leadoff spot (.854 OPS, 15 HR, 13 SB) and Hamilton has been so bad in Triple-A (.311 on-base percentage), though, that the drop-off could be enormous if that is still Cincinnati's plan for next season.

With corner outfielders Jay Bruce and Ryan Ludwick under contract in 2014, re-signing Choo to a multi-year deal that would keep him in center field before taking over for Ludwick in a corner spot down the road is starting to look like a very good option for the Reds.

In the meantime, Hamilton would have a chance to try and regroup with another season in Triple-A while the organization will get one more year to decide if he is part of its future or not. 

Jacoby Ellsbury, OF, Boston Red Sox

So Ellsbury's 2011 season may have been a bit of a fluke. He's probably not going to come close to hitting 32 homers again. Maybe not even half of that.

However, that doesn't mean he's not one of the best leadoff hitters in the game. 

The 29-year-old has reestablished his value with an injury-free season that includes his typical stellar defense, on-base ability (.360 OBP), speed (44 SB) and just enough power (26 2B, 8 3B, 7 HR) to make him one of the best all-around outfielders in the game. 

Having Jackie Bradley Jr. to step into the starting job if Ellsbury signs elsewhere is a nice Plan B, one that most teams lack.

But there's no guarantee that the 23-year-old Bradley Jr., who is just 9-for-58 in the majors this season, will come close to replicating what Ellsbury can do when healthy.  

Curtis Granderson, OF, New York Yankees

Granderson's long absence this season, due to two separate injuries, may have been just as effective as having another 40-homer season in proving his worth.

The Yankees got very little production out of Granderson's replacements after Vernon Wells cooled down from his fast start. 

The 32-year-old Granderson, who has an .881 OPS since returning from the disabled list earlier this month, will still be able to point to his back-to-back 40-plus-homer seasons in 2011-2012 and earn a hefty free-agent deal because of it. 

Finding a lefty power hitter who fits as well into Yankee Stadium as Granderson does will be a tough task for the Bronx Bombers.

Re-signing Granderson could be near the top of their priority list, especially if Robinson Cano isn't brought back.

Hiroki Kuroda, SP, New York Yankees

If the Yankees weren't within striking distance of a playoff spot this late in the season, CC Sabathia's decline would be getting much more attention than it has.

He probably owes a lot of thanks to the always-reliable Hiroki Kuroda, one of the biggest reasons why the Yankees' rotation has held up. 

Signed to a one-year, $15 million deal before the season, the 38-year-old Kuroda has been better than ever in 2013, with a 2.33 ERA in 24 starts. He hasn't had a bad season since coming over from Japan back in 2008, so there wasn't much room for improvement, making Kuroda's 2013 season all the more impressive.

Despite his age, it's likely that some team will be willing to give Kuroda a multi-year deal this offseason.

If the Yankees are unable to re-sign him, they could have much bigger problems than trying to retain or replace their offensive stars. 

Brian McCann, C, Atlanta Braves

Remember when Brian McCann, coming off a mediocre 2012 season (.698 OPS in 121 games), was on the disabled list recovering from offseason shoulder surgery while Evan Gattis was hitting homers in bunches?

Probably not, because McCann has returned to form since coming off the disabled list (.864 OPS, 17 HR) and the rookie Gattis—as is very often the case with younger players who seemingly come out of nowhere—has been brought back down to earth.

While Gattis has improved enough defensively to be a viable part-time option behind the plate, there is no denying how much the pitching staff would suffer from losing McCann, who was named to his seventh All-Star Game back in July.

McCann is the top catcher in available via free agency this offseason—and it's not even close. The Braves will have plenty of competition in signing him to a contract, as McCann will only be 30 years old at the start of the 2014 season and still has plenty left in the tank now that he is fully healthy. 

Ervin Santana, SP, Kansas City Royals

Ervin Santana has either met or even exceeded the expectations that the Royals could've had when they acquired him prior to the season. Now, he'll be much more difficult to re-sign because he could be the top free-agent starter available during the upcoming offseason.

Replacing his production isn't likely to happen. 

In 23 starts for the playoff-contending Royals, the 30-year-old Santana has a 3.25 ERA with a 74 percent quality start rate and an average of 6.7 innings per start. He's also allowed two or fewer earned runs in 13 of his starts.

While Santana might not have the reputation as an ace or No. 1 starter, his 2013 stats tell a different story and so will his agent when negotiating his next contract.

The Royals, who will likely pick up James Shields' 2014 club option—which will be aaround $12 million—while owing $11 million to Jeremy Guthrie and close to $5 million to Wade Davis, might not have the payroll flexibility to re-sign Santana. 

Even if they did, they might not be able to compete with the big-market teams who'll be bidding on the right-hander.