Buenos Aires: Boca Juniors weathered a whirlwind start from Olimpo to open the defence of their Argentine league title with a 2-0 home win and extended their unbeaten run to 30 matches on Friday.   

San Lorenzo, another of Argentina's so-called Big Five teams, had their hopes of a winning start to the Clausura championship to edge away from relegation danger shattered in a 4-1 defeat at Lanus.   

Olimpo attacked from kickoff and goalkeeper Agustin Orion had to go down sharply at his left-hand post to push away a shot from Martin Rolle and prevent Boca from going behind inside half a minute.   

Urged on by a packed Bombonera bedecked in their blue and yellow colours, Boca found their feet after the opening 10-minute onslaught during which they were mostly forced into their own half and captain Juan Roman Riquelme came in for close attention from Olimpo's defenders.   

Riquelme was involved, however, when Boca broke the deadlock four minutes from halftime. His chipped centre from the left edge of the box was headed down into the middle by winger Pablo Mouche, who looked marginally offside, for striker Dario Cvitanich to blast home.   

Boca, who won the Apertura title by a 12 point margin from their closest challengers in the first half of the season, went further ahead when Riquelme delivered a well-weighted pass to Mouche, who found the net at the second attempt in the 66th minute.   

"It's important to start with a win. We'd gone three or four tournaments without being able to start with a win," Riquelme told broadcaster TV Publica. Boca were held 0-0 at Olimpo in their opening match of the Apertura in August.         

Stunned Saints   

Having had a very poor Apertura, San Lorenzo are in the bottom-four danger zone of the relegation standings, which are based on points averages over three seasons.   

They appeared to have ironed out some problems during the off-season and had made a good signing in former Uruguay striker Carlos Bueno.   

Bueno scored just before the hour on Friday but by then the Saints were four goals down, having conceded three in the opening half hour. Former River Plate striker Mariano Pavone scored twice, including Lanus's fourth early in the second half.   

Lanus had gone into the match determined to erase the bad memory of their round of 32 elimination in the Copa Argentina after losing a penalty shootout to Barracas Central, who are near the bottom of the third-tier Primera B Metropolitana division.    

"We had our revenge," Pavone told reporters.   

San Lorenzo's frustration boiled over in the final quarter of an hour when two defenders, Nicolas Bianchi Arce and Fernando Meza, were sent off.