Let's say your team has a 25 year old ace with a history of arm trouble. Let's also pretend your ace pitched more innings than ever last year . . . by a lot. And, many of those innings were high pressure, as your team was skilled and lucky enough to make it to the playoffs and win the championship. Amazingly, your young ace was unbelievable in the post-season, despite being new to October play and the pressure that comes with it.
Now let's say that your ace, who signed a bit of a discounted long-term deal in the off-season, no doubt in part because of the history of arm trouble that he's had, shows up in spring training and within a couple of weeks is complaining of tightness in his throwing elbow. He has the elbow checked out by a doctor synonymous with "out 3 to 6 months" and miraculously is pronounced healthy with no structural damage.
You're out of the woods (for now). Except you still need to get your ace into regular season shape while making sure the tightness (or any other problem) doesn't re-appear. He makes a few starts in low-pressure spring games, and in his last exhibition start, he throws 83 pitches, giving up 6 earned runs in 5 innings. Not a bad performance, especially with 7 strike outs. But, not great either.
You now have to think of the regular season and when he makes his first start. You look at your calendar and see that games 4 through 6 of your season are being played at an extreme hitter's park that messes with pitchers' heads about as much as it messes with their stuff. True, the park isn't as bad as it has been in years past, but it's still one of the most hitting-friendly parks in the majors.
Just past those three games are three more games in a basically neutral park. It's new and doesn't have any history of ripping into the psyche of pitchers. If anything, it has a reputation of being a bit of a pitchers' park, even if the numbers don't bear that out.
One more factor to add in here: your ace has never in his career pitched in the hitters' park or, in the regular season, against the team that plays in the hitters' park. On the other hand, your ace has a 0.00 ERA, 0.98 WHIP, and 17 Ks in 14.3 innings at the neutral park. Against the team that plays in the neutral park, your ace has a career 2.04 ERA, 1.06 WHIP, and 83 Ks in 79.3 innings.
With all this information, when do you get your ace his first regular season start?
If you're the Phillies, you pitch Cole Hamels in Colorado (the hitters park) in game 4 rather than waiting three to five games to pitch him in Washington (the neutral park). And that's just idiotic.
Hamels dominates the Nationals, even more so at Nationals Park. He obviously feels comfortable against the team and in their park. On the other hand, he has faced the Rockies only once, losing to them in the post-season in Philadelphia. He has never faced the team in the regular season, and has never pitched in Colorado.
Why in the world risk his precious, fragile arm in an environment that is known for torturing pitchers, even if less so now than several years ago? Why risk him compensating for ineffective stuff (something Colorado is known for) by altering his mechanics even slightly? Why risk him overthrowing to make up for the combination of rust and altitude? Why take any gamble with this rarest of commodities, a young lefty dominant ace, in the first week of a 162 game season?
There's just no reason to start Cole Hamels' season in game 4 in Colorado rather than in games 7 through 9 in Washington. Even if the start turns out fine, the risk isn't worth it, and the Phillies are being incredibly stupid with the future of the franchise.