Dani Parejo has joined Villarreal on a four-year contract, leaving rivals Valencia where he was captain.
The transfer became the second between the two clubs to go through on Wednesday, with Parejo following Francis Coquelin to El Madrigal - reportedly for a cut-price combined fee of just €13million.
Valencia have already sold Ferran Torres to Manchester City in recent weeks and pressure appears to be building on owner Peter Lim.
Club great Santiago Canizares questioned "the sale of your two best midfielders", with new head coach Javi Gracia yet to take charge of a competitive fixture.
Parejo played 383 times for Valencia since signing from Getafe in 2011 and had spoken of wanting to retire at the club despite reports of his looming departure.
However, Torres, following his move to City, said Parejo "wasn't a good captain with me".
"He's a great player but I never had a relationship with him," winger Torres said of the 31-year-old.
Valencia released a short statement as Parejo's departure was confirmed, thanking the player for "all his effort and commitment", echoing the response to Coquelin's move.