MILAN, April 20 (Reuters) - Inter Milan took a big step towards retaining their Serie A title when Julio Cruz's header sealed a nervous 1-0 win at Torino on Sunday. Roberto Mancini's side have moved six points clear of second-placed AS Roma, who drew 1-1 at home to lowly Livorno on Saturday and lost Francesco Totti to a serious knee injury. With four matches left, Inter would have to completely lose their way to lose the scudetto now, although they meet rivals AC Milan in two week's time. Gianni De Biasi, starting his third stint in charge of Torino, saw his struggling side put the visitors under severe pressure but Cruz's near-post diving header from a corner on half an hour was just enough for Inter in the driving rain. Mario Balotelli hit the post in the first half for Inter but otherwise Torino were on top and had a strong shout for a penalty turned down. Earlier, Juventus striker Alessandro Del Piero hit a hat-trick in a 4-0 victory at Atalanta, which means third-placed Juve are almost assured of a Champions League qualifying place. The 33-year-old, who looks set to miss out on Euro 2008, again reminded Italy coach Roberto Donadoni of his worth with a close-range effort, a cool finish and a fierce shot which brought him his 17th goal of the league campaign. Kaka also scored three, including two penalties, to help AC Milan keep their Champions League qualification hopes alive with a 5-1 win over relegation-threatened Reggina. Milan in fifth are 12 points behind Juventus with four games left but cannot overhaul their rivals because of their inferior head-to-head record against Juve. Sixth-placed Sampdoria, on the same points as Milan, won 3-0 at home to UEFA Cup hopefuls Udinese and can theoretically catch Juve, whom they host in the final game of the season. Fiorentina, in the fourth and final Champions League spot, are four ahead of Milan and Samp after beating Palermo 1-0 on Saturday. Sampdoria travel to Florence next weekend. Cards flew at the other end of the table where Cagliari had two sent off but moved further from the drop zone with a 2-0 win over lowly Empoli. Strugglers Catania beat nine-man Lazio 1-0 thanks to Gionatha Spinesi's first-half penalty but Parma had three dismissed in a 2-1 home defeat by Napoli and remain in trouble. Livorno, Empoli and Reggina are in the relegation zone, all with 30 points. Parma are one point above, Torino are four clear while Catania and Cagliari have a five-point cushion.