Rihanna's 'Last Girl on Earth' tour is gearing up to be one of the hugest blockbuster events this summer, but it looks like the show has lost one of its primary attractions. Young Money's Nicki Minaj has pulled out of the tour, citing the need to finish work on her debut album. This leaves Rihanna and current Top 40 sensation Ke$ha to hold it down. Minaj, of course, took to Twitter to let fans know the bad news.

"Barbz I'm sorry 2 say I will not be going out on RiRi's tour," wrote Minaj earlier today. "I've decided 2 use that time 4 the completion of my album. Hope u understand."

While such a large tour would most likely do wonders for Minaj's career, so would having an actual album to her name. For now, we'll call this one a wash. The tour will continue without the 'Massive Attack' vixen, hitting 25 arena stops all over the U.S. and Canada, including major shows at huge venues like New York City's Madison Square Garden and the Staples Center in Los Angeles.

"We've never done a tour to this capacity," explained Rihanna in a recent interview with AOL Music. "The production is unbelievable and the costumes, we just took it to a whole new level. Visually and sonically it's going to be a big step up from the last time. We just keep growing and this time it is a massive production that I cannot wait for."