SANTANDER, Spain — Christmas was the last straw. Agustín Fernández, a powerful defender for the Spanish soccer club Racing Santander, had gone four months without seeing a paycheck, so while corporate mismanagement had left his team on the brink of insolvency, Fernández was the one going broke.

When the holidays arrived and he could not afford to buy his 3-year-old daughter the bicycle she wanted, the realization nearly left him in tears.

“It made me sick that I could not stand up for her as a man,” said Fernández, who was supposed to be earning about 2,800 euros, or about $3,900 a month. “This is professional football. How could this happen?”

Fernández, who left Santander in January for a lower-ranked team (and the promise of regular pay), is hardly alone in his frustration. While most soccer fans are focused on the glamour of big-money clubs like Real Madrid, Chelsea and Paris St.-Germain, unpaid wages are a growing concern among professional players. The reasons vary — corrupt executives and overspending in the pursuit of trophies are just a couple — but the problem reflects larger economic turmoil.