That was lackluster compared to Ferrell's 2006 NASCAR parody "Talledega Nights: The Ballad of Ricky Bobby," which opened at $47 million, and last year's figure skating comedy "Blades of Glory," which earned $33 million in its first weekend.
Box office analysts said "Semi-Pro" likely suffered because it was released during a normally slow season and was rated R, while "Talledega Nights" and "Blades of Glory" were rated PG-13.
"Will Ferrell is always a draw and audiences love him. But this particular weekend is not quite as strong as his earlier efforts," said Paul Dergarabedian, president of the box-office tracker Media By Numbers LLC.
New Line representatives declined to comment. Last week, media conglomerate Time Warner Inc. announced that New Line would be merged with its Warner Bros. Entertainment studio to cut costs and improve profitability.
Last weekend's top film, the Sony Pictures terrorism thriller "Vantage Point," dropped to second place with $13 million in ticket sales, bringing its two-week domestic total to $41 million.
Sony's new release "The Other Boleyn Girl" performed better than expected, opening at No. 4 with $8.3 million at 1,166 theaters. Its $7,118 per theater average outdistanced other movies in the marketplace.
The weekend's other opening, the Summit Entertainment fantasy romantic comedy "Penelope," debuted in eighth place with $4 million.
Box office revenues overall were down for the third straight week. The top 12 movies grossed $81 million, down 10 percent from last weekend and 25 percent from the same weekend in 2007.
Estimated ticket sales for Friday through Sunday at U.S. and Canadian theaters, according to Media By Numbers LLC. Final figures will be released Monday. 1. "Semi-Pro," $15.3 million. 2. "Vantage Point," $13 million. 3. "Spiderwick Chronicles," $8.8 million. 4. "The Other Boleyn Girl," $8.3 million. 5. "Jumper," $7.6 million. 6. "Step Up 2 The Streets," $5.7 million. 7. "Fool's Gold," $4.7 million. 8. "Penelope," $4 million. 9. "No Country For Old Men," $4 million. 10. "Juno," $3.4 million.
Universal Pictures and Focus Features are owned by NBC Universal, a joint venture of General Electric Co. and Vivendi Universal; Sony Pictures, Sony Screen Gems and Sony Pictures Classics are units of Sony Corp.; DreamWorks, Paramount and Paramount Vantage are divisions of Viacom Inc.; Disney's parent is The Walt Disney Co.; Miramax is a division of The Walt Disney Co.; 20th Century Fox, Fox Searchlight Pictures and Fox Atomic are owned by News Corp.; Warner Bros., New Line, Warner Independent and Picturehouse are units of Time Warner Inc.; MGM is owned by a consortium of Providence Equity Partners, Texas Pacific Group, Sony Corp., Comcast Corp., DLJ Merchant Banking Partners and Quadrangle Group; Lionsgate is owned by Lionsgate Entertainment Corp.; IFC Films is owned by Rainbow Media Holdings, a subsidiary of Cablevision Systems Corp.