Sylvester Stallone's "The Expendables" may have dominated last weekend's box office, but it looks like it's in a major battle to stay on top versus the unexpected challenge of "Vampires Suck."

Fueled by teenage girls willing to laugh at the melodrama of "The Twilight Saga," "Suck" found another $4.4 million on Friday after collecting $6.3 million since opening on Wednesday.  It could come close to $14-15 million for the weekend a 5-day total of $21 million.  

"Expendables," on the other hand, had a massive  Friday to Friday drop for just $5 million and a new 8-day total of $52.7 million.  It will be a close call as to whether either the action adventure or the comedy spoof can hit $15 million for the weekend.

Among other openers, Bow Wow's "Lottery Ticket" is looking at a $3.8 million Friday and an $11 million weekend.  Not exactly Tyler Perry numbers, but not a disaster for the African-American targeted comedy either.

"Piranha 3D" may have won over critics for its campy-ness, but it may have been too little too late.  The delayed horror flick sound $3.6 million Friday for what could be $9-10 million weekend at best.  And as evidenced by Scott Pilgrim vs. The World" (only $1.6 million Friday), moviegoers may not be listening to critics by the end of the summer.

Another disappointment was "The Switch," which should have been titled "Love Happens 2" for Jennifer Aniston.  Like the not-so romantic comedy last fall, "Switch" found only $2.8 million on its opening day for what should be a $7-8 million debut.

After grossing a solid $14 million for the original "Nanny McPhee" four years ago, the sequel, "Nanny McPhee Returns," opened to only $2,7 million Friday for a $9-10 million opening.  So much for American Maggie Gyllenhaal livening up the box office returns.

Look for updated box office estimates Sunday on HitFix.