PREVIEW-Soccer-Boca must adapt to life after Riquelme

BUENOS AIRES, Aug 2 (Reuters) - South American champions Boca Juniors will start adapting to life after Juan Roman Riquelme when they open their Argentine Apertura championship campaign on Sunday.

Riquelme inspired Boca to victory in the Libertadores Cup in June, scoring eight goals on the way, but his spell on loan from Spanish club Villarreal ended after the two-leg final against Gremio.

Boca are still hopeful of securing a further loan period for the mercurial midfielder since Villarreal have announced that he does not figure in their plans and no other European club has publicly come forward.

But, at least for Sunday's home game against Rosario Central, Boca will have to do without him.

"There isn't a player who can replace him," said striker Martin Palermo. "We will have to work harder."

The club hope to renew the loan before the Aug. 17 deadline.

Boca are seen as the main challengers to champions San Lorenzo, who begin their title defence away to Newell's Old Boys the same day.

Ramon Diaz's team have repatriated striker Bernardo Romeo, previously with Osasuna in Spain, and midfielder Daniel Bilos from Mexico's America.

The tournament kicks off on Friday with Colon hosting Velez Sarsfield and Banfield facing Diego Simeone's Estudiantes de La Plata, who won last year's Apertura.