The long-running probe relating to Herrera follows claims the result of a La Liga match in 2011 between Real Zaragoza and Levante was manipulated when he was a player with the former club.
Zaragoza won the game 2-1, which helped them avoid relegation and sent down Deportivo La Coruna, but there are allegations of cash payments made to Levante players.
Chile international Sanchez, meanwhile, accepted a 16-month suspended jail term for undeclared income instead of attending a trial in Spain.
Sanchez faced a court appearance over unpaid taxes of £886,000 from image rights deals during his time at Barcelona as he became the latest high-profile player to be hit by the country’s tax laws.
He pleaded guilty, and in addition to the suspended sentence the 29-year-old, who earns £14m a year at Old Trafford following his switch from Arsenal, has been fined £525,000 and ordered to pay the tax he owes.