Sanz has followed Julen Lopetegui to West Ham, where he is now assistant manager.
“I have really enjoyed it at West Ham so far, because I have arrived at a great Club with great supporters, a beautiful stadium and I am very happy to be here,” Sanz confirmed to the club's website.
“West Ham for me is a big, historic Club in England. They have won multiple European cups, such as the Intertoto Cup, the European Cup Winners’ Cup and the Conference League, and I always remembered the atmosphere at London Stadium when we played there with Sevilla.
“I am very excited because I think the Premier League is the best league in the world and I am very happy to be working here.
“There are six people in Julen’s staff, and we are here to help him to manage the team, to make team talks and to form the training sessions. We want Julen to be comfortable with us doing our job.
“I was a football player at Barcelona, and when Johan Cruyff arrived he changed the mentality for everyone. It was an important time, and when I think football changed, and as a coach you have to know your players and how to manage the team. It is very important to know the players and to be able to implement a philosophy, which is what we’re looking to do.
“I have worked with Julen for ten years, but I have known him for nearly 30. I played with him at Rayo Vallecano, and for me Julen is my boss, my coach, my friend and my brother. I know a lot about Julen, and this is very important when we work together at this Club.”