PREVIEW-Soccer-Argentine pair in danger of Libertadores exit

By Brian Homewood

RIO DE JANEIRO, May 20 (Reuters) - Titleholders Boca Juniors and their fellow Argentines San Lorenzo both face an uphill struggle in the second legs of their Libertadores Cup quarter-final ties this week.

The two sides were held at home in last week's first legs and will need either a win or a high-scoring draw in difficult venues to progress against Mexican debutants Atlas and Ecuadorean champions LDU respectively.

Boca, who drew 2-2 with Atlas last week, visit Guadalajara's Jalisco stadium on Wednesday and will have to do much better than on their visit in the group stage of the competition, when they were comprehensively beaten 3-1.

With playmaker Juan Roman Riquelme still not 100 percent fit and striking pair Martin Palermo and Rodrigo Palacio in erratic form, Argentina's most popular club, six times Libertadores champions, will depend heavily on their experience in the tournament.

"It's a difficult venue but Boca have players with experience, who are used to this type of game, and that makes me confident we can still qualify," said forward Jesus Datolo.

San Lorenzo, who drew 1-1 with LDU in their first leg, face the added difficulty of playing at 2,800 metres above sea level in Quito at a stadium where two other Argentine sides, Arsenal and Estudiantes, have already been beaten this year.

However, Ramon Diaz's team, who are desperate to celebrate their centenary by winning the tournament for the first time, have already shown the dangers of writing them off.

In the group stage, they hit back from 2-0 down to win 3-2 away to Real Potosi, despite playing at nearly 4,000 metres above sea level.