AceShowbiz -

Jake Gyllenhaal apparently is back on the market. Us Weekly reports that the star of "The Day After Tomorrow" has split from Sports Illustrated model Alyssa Miller after six months of dating. The couple's heavy workload reportedly contributed to the separation.

"They fizzled out. It happened a while ago - before the holidays. He's back on the scene," a source said. Another source close to the duo explained, "Things were really good between Jake and Alyssa right up until he had to leave for L.A. to go shoot a movie ['Nightcrawler'] in the fall. Then the distance just really got to them."

"They were apart for the holidays, and things weren't good with them even before that. She's very much a long-term relationship girl. He's not as much of that mindset," another source said of the couple, while another added similar info, saying that Gyllenhaal "was very taken with [Miller], but I think their work definitely drew them apart."

Gyllenhaal and Miller reportedly met for the first time at a gym last year. The 33-year-old actor is now busy filming his latest flick "Nightcrawler". The thriller tells the story of a freelance crime reporter who discovers the underground world of L.A. He plays alongside Rene Russo and Bill Paxton among others.