I'd like to answer this question by using my favorite pitcher stat, Opposing OPS. OPS (On-base Plus Slugging percentage) has gained wide acceptance for evaluating hitters, but it is also a good stat to use for pitchers. In the past, batting average was the most common stat for hitters and ERA most common for pitchers. But unlike batting average, ERA is really a pretty good indicator of overall effectiveness for pitchers. Nevertheless, opposing OPS is one-step better. It eliminates a lot of the luck elements inherent in ERA. A couple of these elements are the effectiveness of relievers and the timeliness of hits.
Let's evaluate Peavy in this context. Opposing OPS over the last five years, using only starters with 100 or more starts, and only pitchers who played in 2008. By doing this, we are considering long-term effectiveness, durability, and limiting our analysis to active pitchers.
Here are the top ten pitchers in this context:
| Pitcher | Games Started | ERA | OPS |
| Johan Santana | 168 | 2.82 | .621 |
| Jake Peavy | 150 | 2.95 | .647 |
| Roy Halladay | 136 | 3.23 | .650 |
| Chris Young | 117 | 3.72 | .664 |
| John Smoltz | 105 | 3.15 | .666 |
| Carlos Zambrano | 161 | 3.45 | .667 |
| Brandon Webb | 169 | 3.30 | .668 |
| Ben Sheets | 128 | 3.24 | .669 |
| Randy Johnson | 142 | 3.77 | .672 |
| CC Sabathia | 158 | 3.40 | .675 |
Based on these factors, it's clear that Johan Santana is the best, but Jake Peavy, even considering that he has played in a pitcher's park, is on the exclusive list.
If you lower the limit to 50 starts in the last five years, here's what you get:
| Pitcher | Games Started | ERA | OPS |
| Rich Harden | 88 | 3.06 | .614 |
| Johan Santana | 168 | 2.82 | .621 |
| Tim Lincecum | 57 | 3.16 | .636 |
| Jake Peavy | 150 | 2.95 | .647 |
| Chris Carpenter | 97 | 3.11 | .649 |
| Roy Halladay | 136 | 3.23 | .650 |
| Chris Young | 117 | 3.72 | .664 |
| John Smoltz | 105 | 3.15 | .666 |
| Carlos Zambrano | 161 | 3.45 | .667 |
| Brandon Webb | 169 | 3.30 | .668 |
Source: Baseball Info Solutions.
The effectiveness of Rich Harden becomes obvious here. A healthy Rich Harden might be the best pitcher in baseball. If you are looking for youth, Tim Lincecum is your choice.
Apology to my radio listeners: In my radio Stat of the Week this past Tuesday on 670 the Score in Chicago, I inadvertently mixed up Opponent OPS with Opponent Slugging Percentage. For example, I said that Carlos Zambrano was the number one pitcher in Opponent OPS over the last five years. He's actually number one in Opponent Slugging Percentage and number six in Opponent OPS. My apologies!