Last week, the pair was spotted sharing a cozy meal at the W Hotel in Barcelona, and the singer, 33, and the athlete, 23, get thisclose in Shakira's upcoming video for her song "Gypsy," premiering in April.
"They were giggling. They're very flirty," a source tells PEOPLE of the video shoot. "They had a lot of chemistry while they were filming."
Absent from the set to witness said chemistry? Shakira's longtime love Antonio de la Rua, and Maria Francisca Perello, whose relationship with Nadal went public last summer.
Nadal's rep has denied a romantic relationship between the pair and Shakira's rep describes them as "good friends."