28-year-old William had been expected to leave the Seville club this summer for the Premier League.
However, the arrival of Manuel Pellegrini as head coach at Betis has changed plans.
Pellegrini admires the qualities of William, a Euro 2016 winner with Portugal, and wants to keep him.
Since arriving at Betis from Sporting CP in 2018, William has not reached the level expected, but has shown flashes of great quality.
Pellegrini counting on William
Betis paid €16m plus €4m in bonuses for William and rated him at €35m a year ago.
The Covid-19 pandemic has affected their valuation, but they would still expect at least €20m to sell William.
Pellegrini knows that for Betis to return to Europe, having players of William’s quality is essential.
As a result, he hopes to hold on to the sturdy midfielder, although a big offer would make Betis seriously consider a sale.
Angola-born William has made 56 appearances in the green and white of Betis.