LaLiga announced last week that Barcelona's away game at Villarreal will take place in the United States on December 20th, in the first European league fixture to be held abroad.
The Spanish Footballers' Association (AFE) said Friday there would be a "symbolic protest" at the start of every La Liga match this week.
Players from both Oviedo and Espanyol refused to move for the first 15 seconds of their game on Friday, although broadcasts of the game did not show this.
"We are against the match, we believe it distorts the competition," Madrid coach Alonso told a news conference.
"There hasn't been unanimity or consultation for it to be played on neutral ground. The protests are positive, and that sentiment is positive.
"We believe it could happen if there were unanimity, but that's not the case."
LaLiga leaders Real Madrid face Getafe on Sunday, and Alonso said striker Kylian Mbappe should be ready to play.
The French superstar has endured ankle discomfort over the past fortnight and missed France's World Cup qualifier against Iceland on Monday.
"Everyone who went with their national teams, except Dean (Huijsen), has returned in good condition," said Alonso.
