Ryan Vogelsong had a career year in 2011.
He stepped into the rotation for an injured Barry Zito and quickly established himself as a big-time pitcher.
Vogelsong's career renaissance earned him a host of career-best numbers and a trip to the All-Star game.
Was this year a flash in the pan, or a sign of things to come for an improved pitcher?
Here are five reasons that the Giants should not expect a repeat of this season's performance.
In this day and age advanced baseball statistics provide an absurd amount of information.
You seemingly can find evidence to support virtually any claim, positive or negative, about a player's production.
The same is true of Ryan Vogelsong.
While you could pick apart his various splits and point to all of his glowing achievements this season, they also reveal potential pitfalls for 2012.
Looking through Vogelsong's sabermetrics reveals two areas in which he was the beneficiary of a little luck in this season.
The first telling stat is Batting Average on Balls In Play, or BABIP for short.
For a proper frame of reference consider the following information from fangraphs.com:
"The average BABIP for pitchers is around .290 to .300, and pitchers have much less control over their BABIP than batters. To what degree pitchers can influence their BABIPs is still up for debate, but even dominant pitchers have average career BABIPs that deviate just slightly from the .290 to .300 range."
Vogelsong's .285 BABIP this season is not ridiculous, but it is safe to assume that this number will rise closer to the norm.
The second notable area can be seen in opposing batters' numbers with two outs and runner(s) in scoring position (RISP).
Opponents hit only .153 with a .216 BABIP with two outs and RISP. The batting average against in this situation is 91 points lower than the overall average of .244.
This represents a remarkable combination of clutch pitching with some added luck from the BABIP.
Whether you cite luck, or clutch pitching, Vogelsong will be hard-pressed to maintain that level of effectiveness next season.
It is not unusual for rookie pitchers to perform very well their first time through the league before faltering later on.
Major League hitters make adjustments, just as pitchers do.
As scouting reports grow in detail and film on tendencies pile up, hitters take note.
Ryan Vogelsong is not a rookie, but the 2011 season was his first big league action since 2006 and he pitched like a brand new player.
It is reasonable to assume that when Vogelsong returns to the mound that opposing batters might be better prepared to face him.
Another statistical breakdown worth noting are the differences between Ryan Vogelsong's first and second-half numbers.
Prior to the All-Star break, Vogelsong boasted a 6-1 record and a stunning 2.17 ERA.
This incredible start to the season is what earned him a spot at the Midsummer Classic.
Following the break Vogelsong pitched well, but was not quite as dominant.
During the second half of the season he posted a 7-6 record and 3.26 ERA.
Don't get me wrong, a 3.26 ERA is still quite impressive, but it is over a full run higher than his first half production.
Did Vogelsong tire slightly down the stretch, or was he simply coming back to earth?
Ryan Vogelsong is already 34 years old.
Throughout baseball history there have been a number of crafty old left handers who have continued to pitch well beyond their prime playing age.
The difference here is that Vogelsong is a righty.
It's rare to see a right-handed pitcher maintain dominance as his "stuff" declines.
While Vogelsong is not considered a power pitcher, continuing to lose zip off of his fastballs won't help.
He throws both four and two-seam fastballs and they are his bread and butter pitches. In 2011 fastballs accounted for 70 percent of his pitches.
Vogelsong had a breakout season, but will have a difficult time improving, or even maintaining current levels of production as he ages.
The final and most obvious reason to question Ryan Vogelsong's ability to repeat is his track record.
His previous career best in ERA was 4.43 back in 2005 as a reliever for the Pittsburgh Pirates.
Following his stint with the Pirates, Vogelsong went on to play in Japan for three years.
In 2010 Vogelsong returned to the United States.
Nobody can take away Vogelsong's 2011 season, or his story of perseverance and redemption.
However, Vogelsong's career offers no reason to believe that he will be able to maintain his new-found success in 2012.