The heavily-fancied side were beaten 2-0 by the African nation in a warm-up game, and their coach has confessed that they must get better if they are to challenge in London
The world champions have selected a strong squad for the London Games, and have been tipped as one of the favourites for gold medal in the competition.
However, the side’s trainer has confessed that more work is needed before the tournament starts.
"We came up against a rival whom I congratulate,” the 46-year-old said at a press conference after the game.
“I think we must be realistic and know that these difficulties will be presented at the Olympics, with fast and strong players. We have not been accurate and we have to improve.
"We have played a warm-up game and expect to be better than we were today, but I think we must be positive. The boys have tried, but we have not been good with the ball, and Senegal had the beating of us physically,” he explained.
Milla went on to state that his side should not be compared to the Euro 2012-winning senior team.
"We've talked; the teams are not comparable. The senior team are making history, but we are also looking to achieve success.
“However, we have some similarities because we too have players who can control the game and take the initiative,” the coach said.
Spain start their Olympics campaign against Japan on July 26.