Fabio Felline (Androni Giacattoli-Venezuela) finished second, and Giovanni Visconti (Movistar) finished third. Luca Paolini (Katusha) remains the maglia rosa.

It rained overnight, but by race time, the roads were dry enough to be a nonfactor. In the first few kms, Julien Berard (Ag2r-La Mondiale), Emanuele Sella (Androni Giacattoli-Venezuela), Miguel Minguez and Ioannis Tamouridis (both from Euskaltel-Euskadi), Johan Le Bon and Anthony Roux (both from Francaise des Jeux), and Pim Ligthart (Vacansoleil-DCM) escaped and ran up a nearly eight-minute lead before the peloton, led by Katusha, woke up.

At 151 kms, the break's lead was down to four minutes, and Le Bon, Ligthart, and Minguez dropped their companions, although Berard did join them. Vini Fantini joined Katusha at the front, and the four leaders' advantage was down to one minute when Minguez and Berard dropped Le Bon and Ligthart at the base of the Category 3 Vibo Valentia. Berard was dropped and caught by Ligthart and Le Bon, while Minguez went solo.

It began to rain, but the pursuit was relentless, despite a crash with about 60 km left. The peloton captured Minguez with 42 kms to go, and Patrick Gretsch (Argos-Shimano) countered. Stefano Pirazzi (Bardiani Valvole-CSF Inox) joined the German, but the peloton, which had splintered on the climb, reeled in the pair quickly.

The weather worsened, and Vincenzo Nibali (Astana) puncture, although he rejoined the peloton quickly. Leonardo Duque (Colombia) attacked on the descent. He was reeled in, but Gretsch had another dig, and Frederik Willems (Lotto-Belisol) joined him.

At the base of the descent, the weather improved and something of a regroupment occurred. With 25 kms remaining, Gretsch and Willems led the bunch by 0:30. Bardiani Valvole-CSF Inox set a stiff tempo, however, and the pair was reeled in.

Pirazzi and Marco Mercato (Vacansoleil-DCM) attacked, and three other riders joined them. On the day's last climb, the Category 2 Croce Ferrata, the weather worsened. The others dropped back, but Mercato forged ahead. Sylvain Georges (Ag2r-La Mondiale) caught and dropped the Italian. Behind, Katusha rode herd over the peloton.

Georges forged a one-minute lead over the field. With 15 kms left, Sky took over at the front and paced the peloton up the climb. The heads of state assumed their positions at the front, while rider after rider was shelled. Danilo Di Luca (Vini Fantini-Selle Italia) attacked, and Robinson Chalapud joined him.

The pair dropped Georges. With Di Luca doing most of the work, the fugitives led the field by 0:10 with five kms left. The 2007 Giro champion dropped Chalapud, but the peloton was relentless. It reeled in Di Luca with 500 ms remaining. With 300 ms left, Battaglin burst out of the peloton for the win.

According to Battaglin, the stage was tailor-made for him. "I was good yesterday," he said, "but in the end it felt more like a Moto GP than a bike race, and I was dropped. Today, the climb suited me, the rain might have stopped some riders, and the gradient wasn't too hard, and even though I attacked a bit early, it went well.

"In 2011, after I had won everything as an amateur, I started my pro career winning at the end of 2011 [he won the Coppa Sabatini in 2011]. Perhaps I thought it was easier than it really is. I may have paid for that last year [no wins in 2012]. This year, I was determined to show I am a good rider. I worked hard in the winter, and I'm starting to reap the rewards."

In the overall, Paolini leads Rigoberto Uran (Sky) by 0:17 and Benat Intxausti (Euskaltel-Euskadi) by 0:26. Stage 5 will be a flattish, 203-km ride from Cosenza to Matera. The stage will have an uphill run to the finish that might drop some sprinters. Who will win? Check in at www.roadcycling.com and find out!

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