The Rams have pulled off a coup by signing the midfielder from Spanish giants Real Madrid, with the 21-year-old having made his La Liga debut when coming on to replace Mesut Ozil in a 4-2 win over Osasuna on the final day of the 2012/13 campaign and being a regular starter with the club's B and C teams.
"Derby County is a great option for me," said Mascarell. "Obviously, the Premier League is more famous in Spain, but we can still see the Championship and study it, so I know all about it.
"It's a very important year for me and one of the most important things was knowing Steve McClaren wants to play good football. It will be a good chance for me to grow as a footballer, given the way he likes to play."
Mascarell, who travelled with Real for the International Champions Cup in America and featured against Roma and Inter Milan, has represented Spain at youth level, as well as being called up by Equatorial Guinea for two World Cup qualifiers before declining to play.
When asked about his experiences at the Bernabeu, he told Rams Player: "As long as you train hard and work hard, you'll find that Real Madrid will look after you, so the most important thing is to make sure you focus on your football and everything else will be fine.
"I'm now looking forward to living in England, it's a fantastic league and a great country to live in. It will also give me the chance to learn English, which will help me develop as a person.
"I started off in a small village in Tenerife, then had my football education at Laguna, before my agent took me to Real Madrid, where I've been for four years. Obviously, that move helped me make plenty of improvement and now I've got the chance to play for Derby County - where I have great expectations as well.
"My best position is in front of the back four, so the play can come through me and I can pass it around and control the pace of the game, so I'm sort of like the organiser of the team."