In the footballing world, players are allowed to switch clubs and loyalties during the transfer windows -- at the end of the season and in January. And, with that comes the freedom for players to wear jerseys of more than one club at the European stage.

As the Champions League quarter-finals between Barcelona and Paris St Germain kicks off tonight, Rediff.com showcases those players who've donned the colours of both clubs.

Richard Dutruel

The goalkeeper started his career with Paris St Germain and went to represent the French club from 1991-1996. After plying his trade at Celta Vigo later, this Frenchman then went on play at Barca from 2000-2002 at the death of his career. He was the No 2 'keeper to Pepe Reina while playing the Catalan club.

Another Frenchman, he spent eight successful seasons at French club Lens. The central midfielder was then was sold to Barcelona in 1999 but was used very sparingly in the only season he represented the Spainish club.

He was then snapped by Paris St Germain for 6 million Euros the next season and was marginally successful, winning the domestic Cup in 2004, his last season there.

The current vice-captain of Arsenal, Arteta was part of Barca's youth team in the early part of the last decade.

The medio was loaned out to French club PSG from 2000-2002.

Juan Pablo Sorin

The former captain of Argentina, Sorin heavily served Argentine champion club River Plate Buenos Aires before making the switch to Europe.

He played for an Italian club before being loaned to Barca. The defender played for one season ('02-'03) in Spain and then moved to PSG the following year.

He ended his career with Brazilian club Cruzeiro in 2009.

Ronaldinho 

He was the player who's magical moves brought Barcelona the worldwide appeal it enjoys today.

He was signed for Barca from PSG in 2003, following a two-year stint with the French team.

Ronaldinho was the man responsible for Barca's Champions League triumph in Paris in 2006 and is considered a legend for his contributions to the club.

The attacking midfielder was instrumental in Barca's league title in his debut season -- 2003-'04. He was also the man who propelled the Catalans into the 2006 Champions League final.

His stay at the club was peppered with injuries but he still maintained his starting spot until the arrival of a certain Lionel Messi.

The Frenchman then signed for AS Roma the next season and was then signed for three years by PSG, where he enjoyed decent success.

Thiago Motta

This midfielder, who currently plies his trade at PSG, began his career at Barca.

He was fairly successful in Spain, but was injury-prone.

Maxwell

The Brazilian currently plays as defender at PSG,  a club he signed a 3-year deal with in January last year.

Before this, he played as left winger at Barcelona. He was signed by the Catalans from Inter Milan for three years in 2009.

PSG's Ibra is most likely feature in the duel tonight and it will be interesting to see what he comes up with against a club he shares cold memories with.

He followed Maxwell into the Catalan club from Inter in 2009 and tasted good success despite Messi's massive presence.

It will be interesting to see how he measures up against his former club at the Champions League match tonight.