Mark Cavendish didn't feature in the top placings as stage two of the Tirreno-Adriatico ended in a bunch sprint finish.
Despite losing two minutes waiting for a train at a level crossing, the peloton caught the three breakaway riders well before the end.
Cavendish did suffer problems on the one climb and fell away from the main bunch before then fighting his way back into the pack.
The pace remained high with several attacks before it was left for the sprinters to claim victory.
Tyler Farrar of Garmin-Cervelo took the honours ahead of Petacchi and Haedo.
Cav's normal lead-out man Mark Renshaw finished in fourth place.