The Social Wars broke out during his consulship. His colleague, Lucius Julius Caesar was sent out to face the Samnites, while Lupus was to fight the Marsi. He chose Gaius Marius as his legate. Marius advised him to train his inexperienced troops more before meeting the enemy in battle, but Rutilius ignored this advice. Rutilius advanced and divided his troops with Marius in order to build two bridges to cross the river Liris. The Marsic commander, Vettius Scato, was encamped on the other side. He placed the main body of his troops near the bridge of Marius and sent a smaller detachment to lie in wait near Lupus's bridge. The following morning, Rutilius fell into the trap and lost most of his army; he himself received a fatal wound to the head. Marius noticed bodies floating down the river and so crossed and captured the poorly defended enemy camp.