* Club banned after Cup game boycott
* Players protesting over unpaid wages (Adds FIFPro statement)
MADRID, Jan 31 (Reuters) - Racing Santander have been banned from next season's King's Cup after their players, protesting over unpaid wages, refused to challenge for the ball in Thursday's quarter-final second leg at home to Real Sociedad.
The third-tier team, who were also slapped with a fine, announced as early as Monday they would boycott the game unless unpopular president Angel Lavin and the board, who are widely blamed for the club's financial woes, resigned.
The players formed a line around the centre circle immediately the match kicked off and Sociedad played the ball around in their own half for about a minute before the referee brought the game to a halt.
The Spanish soccer federation (RFEF) confirmed on Friday Santander had forfeited the tie, sending Sociedad, who were 3-1 up from last week's first leg in San Sebastian, through to play Barcelona in the semi-finals.
Santander will not be allowed to compete in the 2014-15 Cup competition, the RFEF added. They did not specify the size of the fine and were not immediately available for comment but local media said it was just over 3,000 euros ($4,100).
The bizarre scenes on Thursday brought the financial difficulties plaguing many debt-ridden Spanish clubs sharply into focus and prompted an outpouring of sympathy for the Santander players and coaching staff.
"Those were the kind of images anyone involved in football never wants to see," Barcelona coach Gerardo Martino told a news conference on Friday.
"It is hard to take in and just makes you want to support the players and coaching staff working there," he added.
"It's normal that when you work you are paid for your efforts and that is not happening at Racing.
"In a situation as important as the quarter-finals of the King's Cup with the tie still alive it was an ugly thing."
FIFPro, which represents the world's professional soccer players, said the incident had not taken them by surprise as players' rights were being "systematically trampled on".
"If we don't change the system, there will be more actions like those of Santander," FIFPro President Philippe Piat said.
"Players are considered to be little more than objects to be used and thrown away," he added.
"This is the result of a deeply flawed and illegal transfer system, which allows clubs to squander money irresponsibly, instead of spending it with good sense.
"The action of the Racing players is a new signal, warning that it's essential to do something urgently in order to save football."
Santander, who are in administration, were relegated from La Liga at the end of the 2011-12 season after finishing 10 points adrift at the bottom and dropped straight down into the third tier (Segunda B) at the end of last term.
Lavin and the rest of the board were voted out of office at a shareholders' meeting on Friday called by the judge overseeing the club's bankruptcy proceedings, local media reported.
Former Santander player Juan Antonio Sanudo has taken over, the reports said. ($1 = 0.7373 euros) (Reporting by Iain Rogers, editing by Ed Osmond)