Bruce Chen got the opening day start for the Royals in 2012, but it wasn’t because he had the best stuff on the pitching staff.
Until rainouts and off-days throw things out of whack, a team’s opening day starter is likely to face the opposing team’s opening day starter in subsequent games, and those can be tough matchups.
A pitcher can throw extremely well for a month and not have much to show for it because he’s constantly matched up with a pitcher who throws even better. Pitching well and still losing can destroy whatever confidence a young pitcher has.