Mantilla is as low-profile as any of the seeds on show despite having been on the circuit for 10 years, spending much of the time in the top 20.
World ranking: 21
US Open best:
4th round (1997)
2002: 1st round
2001: 2nd round
Like most Spaniards his favourite surface is clay, and Mantilla's best Grand Slam moment came with a run to the semi-finals of the French Open back in 1998.
He possesses a fine backhand and, when confident, is capable of picking off winners, despite lacking the power of some of the game's big hitters.
But the 28-year-old's biggest virtue is the consistency of his game, and that proves most effective on clay.
However, despite having no great weapons and suffering a gradual decline in recent seasons, Mantilla has fought back in 2003 with his best form for several years.
He did well to reach the last 16 at the Australian Open, lost to eventual champion Juan Carlos Ferrero in the fourth round of the French Open, and won his first Masters Series title in Rome.
A surprise straight-sets victory over Roger Federer in the final in May was the highlight of Mantilla's career to date.
The time is right to match the fourth round appearance he managed in New York six years ago.