The tension in Spain's team between Real Madrid and Barcelona players could flare up when Jose Mourinho shows up to watch their first European Championship match on Sunday.
The Madrid coach will be at the PGE Arena in Gdansk for the world champions' game against Italy amid a feud between Mourinho and Barcelona midfielder Xavi Hernandez.
A string of ill-tempered matches between the Spanish league rivals had created friction inside Spain's normally tranquil dressing room, as international team-mates were seen brawling at the close of a particularly ugly Spanish Super Cup contest in August.
Xavi recently said in an interview with Spain's Canal Plus TV that Barcelona's 5-0 victory over Madrid in November 2010 created tension in the team. He also criticized Mourinho's tactics despite the pair having worked together at Barcelona when Mourinho was an assistant coach.
"Mourinho won't go down in football history. For me, (Pep) Guardiola is the best and has been over the past four years in charge of Barca because he revolutionized football," Xavi added. "Barca has set a better example than Madrid. We've always been respectful, and them not so much. It's very personal the feeling."
Mourinho replied to Xavi's remarks through Portuguese sports daily Record on Saturday, telling the Barcelona playmaker to focus on "playing football."
Mourinho also said in a statement on Madrid's website that it was his "duty" to be by the side of Madrid's international players at the tournament.
"I'm Portuguese and will therefore hope my national team wins, but I will always support all my players as well," said Mourinho, who will also attend Saturday's Group B match between Portugal and Germany.
In the interview with Canal Plus, Xavi said "there were problems between friends.
"My friendship with Iker (Casillas) goes a long way so that came above everything else," he said. Barcelona defender "(Carles) Puyol and (Spain coach Vicente) del Bosque did a lot to help repair the situation. The press also had a part in it as it created a fictional tension, although it's true that there was tension but just not as much as let on."
Spain is defending its European title. This is the first tournament for the World Cup champions since Mourinho's arrival at Madrid, which edged Barcelona for the domestic title this season.