Pablo Sandoval is entering his last season under team control and that puts the Giants in a tough spot of figuring out whether to offer him a contract extension now or wait until the end of the year.

Andrew Baggarly has speculated that if the Giants don’t get an extension done before the end of spring, this is likely Sandoval’s last season as a Giant. I’m not sure I buy that, but if he has even a decent season it probably means he will be much more expensive.

The idea of extending Sandoval is an interesting question. There is no doubt that he is a very talented player; his 2009 and 2011 seasons were outstanding, his 2012 and 2013 were injury plagued but above average and no one will forget his performance in the Giants’ World Series victory over the Tigers.

On the downside there is the question of his size, which has been an issue since he broke out in 2009 and has gone up and down over his career.

What makes the idea of a long term deal a bit nerve-racking is that he reported to the team much larger than the team would have liked in 2013, and he didn’t seem all that apologetic about that in an interview with Jeff Passan. Without the carrot (no pun intended) of playing for a mega-deal, will Sandoval have the discipline to stay in good enough shape to remain an above average player?

The one bright sign on the weight front, is that this offseason he has done his workouts on his own, without the team guiding his every move. The results are evident in the photo seen here. Perhaps Sandoval will be able to maintain this new routine into the future and end, once and for all, all of the #FatChat stuff.

So now comes the big question, how big of a contract is Sandoval looking at?

Looking for free agent comparables isn’t very helpful because over the last few seasons there hasn’t been an above average third baseman available who wasn’t already into his mid-30s. The last big contact for a third baseman was awarded to Adrian Beltre in 2011. The other possible comparable — and perhaps a better fit — was the extension Ryan Zimmerman signed in 2012 that is just kicking in for this season.

Overall Zimmerman and Sandoval are fairly similar players offensively. Zimmerman has a career triple slash line of .286/ .352/ .477 compared to Sandoval’s .298/ .351/ .476, while Zimmerman is at 120 wRC+ for his career and Sandoval’s is 125. The only divergence is that Zimmerman is the better baserunner and also rates higher on defense (especially early in his career).

The other great thing for this exercise (no pun intended, again) is that Zimmerman signed his contract going into his age 27 season, the same age Sandoval is now. The only downside is that he was still two years away from free agency instead of one for Sandoval, but he was also a better and more consistent player so maybe that cancels out a bit.

Zimmerman’s contact pays him $14M annually from 2014 to 2018 and $18M in 2019, with a team option in 2020 for $18M. There is also a $10M five-year personal services contract tacked onto the end. Overall he is guaranteed $100 million for 6 years.

Using this as a baseline, to sign Sandoval the Giants are probably looking at a deal lasting five-to-seven years, with an average annual value of $16M-$18M a season. This would take him only into his early-30s, however the age curves for players with large body sizes isn’t especially pretty once they reach 30.

If there aren’t any extensions before the end of the year, the 2015 class of third basemen free agents could be the best in years with both Chase Headley and Hanley Ramirez also hitting the market. With no obvious in-house replacement, if the Giants aren’t sold on Sandoval they could try to sign a third baseman who currently plays for a division rival club instead.