After reading this earlier today, it got me interested in what a fair contract extension for Miguel Montero would be after this season.
What's difficult is that there haven't been any players similar to Miggy in terms of performance relative to age and experience that have received contract extensions. The two contracts that I looked at, for comparison sake however, was the one that Brian McCann signed in 2007 and Victor Martinez signed while he was still with the Indians in 2005. I know some may say it's a stretch to compare Montero to Martinez and McCann, but even though Montero's bat isn't on par with the others, I think his overall game with his improving defense (which is probably better than McCann and Martinez ever were) and leadership (for people that believe in the importance of "veteran" leadership) make Montero their equal. In fact, Montero's fWAR is 3.8 compared to McCann's 3.7 this year.
When the 2005 season began, Victor Martinez was going into his 2nd full year as a major leaguer (age 26 at the time) and signed a 5 year deal that included a club option for a 6th year. The deal included a $1mil bonus and salaries of $500K (2005), $800K (2006), $3mil (2007), $4.25mil (2008), $5.7mil (2009), and club option for $7mil (2010). He was not eligible for salary arbitration until 2006.
When the 2007 season began, Brian McCann was in a similar situation as Martinez, 2nd year player (age 23 at the time) and signed a 6 year deal that included a club option for a 7th year. Like Martinez, McCann received a $1mil bonus and salaries of $500K (2007) and $800K (2008) for the first two years, then salaries of $3.5mil (2009), $5.5mil (2010), $6.5mil (2011), $8.5mil (2012), and a club option for $12mil (2013) with a $500K buyout.
Miguel Montero currently is in the 2nd year of arbitration (age 27), making $3.2mil, a similar figure to what Martinez and McCann made in what would have been their 1st years of arbitration on their deals. Considering Montero would be entering the end of his prime years (generally considered 26-28), I think a fair deal for both parties would be a 4 year, $28.5mil deal with a team option for a 5th year. Montero will be starting his age 28 year in 2012, and I broke down the salaries as $5.25mil (2012), $6.5mil (2013), $7.75mil (2014), $9mil (2015) with a team option for $11mil (2016) with a $1.5mil buyout. If the Dbacks exercise the option, it would pay Montero $39.5mil over 5 years, or $29.5mil over 4 years if the Dbacks decline the option.
Since generally catcher's don't age well past 31, this may be Montero's only chance to get a big contract. Montero also isn't on par with Martinez and McCann hitting wise, so he wouldn't be able to get the kind of money Martinez got this past offseason to play 1st/DH a few years from now. I think that's why adding the club option may entice Montero to sign for a little less than he could possibly get if he waited a year to become a free agent. Even though a catcher doesn't have the inherent injury risks of a pitcher, he has gotten hurt in the past, along with injuries to Mauer and Santana, that may motivate him to sign a deal this offseason.