“I haven’t ever seen a pitcher leave Coors Field and become a worse pitcher.”

-- Former Rockies pitcher Shawn Chacon

The Colorado Rockies joined the National League in 1993. In that span, they’ve had six seasons in which a starting pitcher posted an ERA under 4.00 while throwing at least 162 innings.

Ubaldo Jimenez has three of those seasons: a 2.88 ERA in 2010 (the best in Rockies history); a 3.47 ERA in 2009 (the second-best in Rockies history); and a 3.99 ERA in 2008. Since that breakout season in 2008, Jimenez is 51-40 with a 3.52 ERA. Maybe those numbers don’t blow you away.

They should.

Jimenez isn’t just the one Rockies pitcher in their history who has proven he can pitch in Coors Field year after year; he’s one of the best pitchers in baseball.

While Coors Field isn’t quite the softball field it was in the late '90s due to the use of a humidor to slightly limit the flight of flying baseballs, it remains one of the best hitters’ parks in baseball. So while Jimenez’s 3.52 ERA since 2008 ranks 22nd among pitchers with at least 500 innings, his ERA adjusted for home ballpark places him 10th. His ERA since 2008 is better than Justin Verlander’s 3.55. His adjusted ERA is better than Matt Cain or Jered Weaver or Clayton Kershaw or Zack Greinke or Cole Hamels. His slugging percentage allowed is 23 points lower than Roy Halladay’s.

But should the Rockies trade Jimenez? He starts Tuesday at home against the Braves in what could be his final start with the Rockies, if you believe the trade rumors coming true. (“We would have to be absolutely overwhelmed," GM Dan O'Dowd told the Denver Post. "It would have to be a Herschel Walker deal.")

Or in baseball terms, a Mark Teixeira deal.

But if I’m Dan O’Dowd, I’m not looking for any kind of deal. Would the Dodgers trade Kershaw? Would the Giants trade Cain? Would the Phillies trade Hamels? There may be more good pitchers than we’ve seen in many years, but that doesn’t mean you trade a 27-year-old ace with a favorable contract.

Everybody points to the Teixeira deal the Rangers made with the Braves in 2007 when they acquired Elvis Andrus, Neftali Feliz, Matt Harrison and Jarrod Saltalamacchia. While that turned into a nice trade for the Rangers -- especially with the emergence this year of Harrison -- that kind of haul is for a star is actually rare. Look at what the Indians and Phillies got in their Cliff Lee trades.

Anyway, that’s a matter of risk. Maybe the Rockies think they can acquire four good prospects and have three of them develop. My main reason why a Jimenez trade doesn’t make sense is he’s already signed through 2014 to an extremely team-friendly contract:

2011: $2.8 million

2012: $4.2 million

2013: $5.75 million team option

2014: $8 million team option

While that contract makes him more attractive to suitors, it’s also what makes him so valuable to the Rockies: They have an ace signed through 2014 at a relative bargain-basement price, which essentially means the franchise has more money to spend elsewhere on the team.

Maybe the Rockies are focusing on the negatives. After his unbelievable start last season, Jimenez posted a more pedestrian 3.80 ERA in the second half. His ERA is 4.01 this year -- although after a slow start that included some fingernail issues, Jimenez has a 2.56 ERA over his past nine starts, allowing opposing hitters a .240 average and .285 on-base percentage. His average fastball velocity is down nearly 3 mph from last season, so maybe the Rockies have concerns about his long-term success. But I see an excellent strikeout rate, strong peripherals, and a guy who has a 2.28 ERA on the road this season. He seems OK to me, even if he’s throwing 93 instead of 96.

It’s been a disappointing year for the Rockies. Young prospects making the league minimum can be a lustful desire for any front office. But this franchise has had one consistent No. 1 starter in its history. It seems to me that’s the kind of player you keep, not trade away.

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