Porcello hit Zobrist with a high, inside pitch in the first inning of Sunday's game against the Rays. Both benches were warned but Porcello was not ejected.
Porcello was also fined an undisclosed amount for the incident, which was seen as retaliation for an inside pitch by Tampa Bay closer Fernando Rodney to Detroit slugger Miguel Cabrera the previous day. Cabrera ended up striking out, and exchanged words with Rodney on his way back to the dugout.
Detroit manager Jim Leyland said after Saturday's game that "somebody has to pay the price for that."
Leyland said Sunday that it was part of the game.
"Nobody's trying to hit anybody," he said.
Leyland declined comment on Porcello's suspension or the decision to appeal.
Porcello, 4-6 with a 5.21 ERA this season, is available to pitch until the appeal is heard. His next start is scheduled for Friday at Cleveland. Porcello was suspended five games in 2009 for hitting former Red Sox infielder Kevin Youkilis and sparking a bench clearing brawl.