Rangers could face punishment from Uefa, European football's governing body, after Villarreal's team bus came under attack on its way to Tuesday night's Champions' League tie.
Uefa is awaiting a report from their match observer on the pre-match incident, which saw a window of the bus shattered by a missile. Alex McLeish's side went out of the competition on the away goals rule with their heads high, but the club may face action if it can be proved their supporters were behind the attack.
Spanish police clashed with supporters outside Villarreal's stadium, El Madrigal, and Uefa look set to launch an investigation. A spokesman said: "Once we receive a report from the Uefa delegate then we look into what exactly went on.
"We expect that to arrive two days after the game but if these incidents did occur then action is likely to happen. I don't really want to say too much at this time but we are certain to act on the Uefa delegate's report."
Villarreal could also be in hot water, with Rangers' safety chief Lawrence McIntyre citing security for the game in Spain as among the worst he had seen.
An estimated 15,000 Rangers fans travelled to Spain for the second leg of the last-16 tie, even though the official allocation for travelling supporters was just 3,000. Thousands more managed to obtain tickets for home sections of the ground, despite appeals from McIntyre ahead of the game for those without tickets to stay away.
Villarreal added another chapter to their fairytale progress in this season's Champions' League. The modest Mediterranean side, who hail from a small industrial town of less than 50,000 people and have spent most of their history in Spain's regional leagues, have now gatecrashed their way into the top eight clubs on the continent.
Holding a slim advantage after their 2-2 draw in Glasgow two weeks ago, the La Liga side trailed 1-0 at half-time at the Madrigal. But a rare goal from the defender Rodolfo Arruabarrena at the start of the second half was enough to secure the Spaniards a place in the last eight alongside Barcelona and Juventus.
"We are delighted," the Argentinian playmaker Juan Roman Riquelme said. "We have achieved something very important for the club. It wasn't a great game, but what really counts is that we are through to the next round. No one would have believed that at the start of the competition that we were going to make it through to the quarter-finals."
Arruabarrena, who like Riquelme began his career at Boca Juniors, also highlighted the significance of the team's success.
"We have achieved something historic for this club," he said. "Very few clubs are able to reach the quarter-finals in their first season in the competition. That goal was the most important goal I've scored since I've been at Villarreal."
Yet to lose a game in the competition, the team known in Spain as the "yellow submarine" is preparing to torpedo another of Europe's big guns.
"Of course it's important to go down in the history, but we are already thinking about how we can get to the semi-finals," said Villarreal's coach Manuel Pellegrini. "There is no limit to the ambitions of this team. Our dreams are being held in place by the hard work and dedication of the whole squad."
Rangers could confirm Paul Le Guen as their 12th manager within the "next couple of days", according to their former player Artur Numan. The club themselves would only say no movement was expected on Alex McLeish's successor at Ibrox. But Numan is "almost 100 per cent sure" the former Lyon coach will be named this week by the chairman David Murray.
"In the next couple of days David Murray will probably come out with a statement that Le Guen has signed," he said. "Now it's important the team focus on the league and hopefully take second place and Le Guen is probably already looking for players for next year."Reuse content