It is not that he is a different pitcher, per se, in the post season.
The reason could be that post season opponents scout their opponent more closely.
During the regular season, scouting departments are charged with scouting the minors, the majors, their upcoming opponents, checking out talent to sign during the next draft or international scouting period, and some self-scout their own team for comparison purposes and trade value.
But once the post season rolls around, it is all hands-on-deck to get useful stats and materials to the manager.
The Royals admit that they found out that Price was tipping his change up, enough times the Royals hitters could handle it.
As recounted in SI, when pitching from the stretch when he threw a changeup, Price would take an extra deep breath, one where you could see his shoulders shrug, and he would hold his set a beat longer. It appeared to me the Royals knew the changeup was coming when Price was in the stretch. Royals sources confirmed it: Price tipped his changeup—maybe not 100% of the time, but enough for Kansas City to buy in.
There had been rumors about Price tipping his
pitches when he faced Texas in the Division Series. A Toronto source
told me then that such rumors sometimes pop up, and that the Blue Jays
heard that Price had been tipping his pitchers earlier this season when
he was pitching for Detroit, but “we looked into it and didn’t see
anything.”
A pitcher has the advantage on the mound. He knows what he is going to throw and where he wants to throw the ball. The batter is guessing. Most batters try to time the pitcher's fastball, and work back from that speed. But since it only takes a fraction of a second to determine if it is a fastball, cutter or change up, batters have to project the count and situation in order to make solid contact. If a pitcher is tipping off his pitches, then the advantage swings toward the batter.
