Villarreal's Argentine playmaker Juan Roman Riquelme will return to his former club Boca Juniors on loan until the end of the season, says Boca president Mauricio Macri.

"We are delighted because we know what Roman means to the fans," Macri was quoted as saying on the website of Argentine daily Clarin.

"Financially, we made a big effort to bring him here. It was a great feat ... He is a great playmaker and is part of our history."

However, Villarreal president Fernando Roig insisted the deal is not yet closed.

"Nothing has been signed," he was quoted as saying. "It isn't as straight-forward as it seems."

The deadline for registration of players in Argentina expires later on Thursday.

Spanish media reported that the midfielder would receive $2 million to play for Boca in the Clausura championship, which starts this weekend, and the Libertadores Cup.

Riquelme has been sidelined by Villarreal coach Manuel Pellegrini since the start of the year because the club has been unhappy with his level of commitment despite being given privileges not enjoyed by other squad members.

The 28-year-old is one of0 Spanish Primera Liga's most talented players and helped lead Villarreal to the semi-finals of the Champions League last season although he struggled to recover after missing a last gasp penalty in their defeat against Arsenal.

He played an instrumental role in steering Boca to a host of trophies between 1996 and 2002, winning three league titles and two Libertadores Cups.

A masterful display in Boca's victory over Real Madrid in the World Club Cup in 2000 helped persuade Barcelona to buy the Argentine for 11 million euros ($14.28 million) in 2002, but he never won a regular place in the first team.

He was loaned out to Villarreal the following season when Barca signed Ronaldinho and there the team was effectively built around his elegant, unhurried playmaking skills.

An introverted and softly-spoken character, he retired from international football last September after winning 37 caps, saying that criticisms of his performances in the 2006 World Cup in Germany had affected his mother's health.