As recently as October, Bryan Stockton was touting his big plans for a turnaround of Mattel. The toy company’s chief executive told investors that he was planning to increase Mattel’s focus on reviving Barbie and Fisher-Price, core brands that had been in a slump. He outlined efforts to develop new toys and even lured an industry veteran back to the company who had helped reinvigorate Barbie sales once before.

But it appears Stockton has run out of time. On Monday, Mattel announced that Stockton had resigned as chief executive after just three years in the position and would be replaced by interim chief executive Christopher Sinclair.

“Mattel is an exceptional company with a great future but the Board believes that it is the right time for new leadership to maximize its potential,” Sinclair said in a statement.

On Stockton’s watch, profits sagged and some of Mattel’s most iconic toys struggled to remain relevant. Fisher-Price, the company’s baby-oriented toy line, saw sales fall 16 percent in the third quarter. And while Barbie still remains the top-selling doll brand in the world, its fan base is rapidly dwindling. Sales of Barbie tumbled 21 percent in the third quarter as the company said that fresh marketing and product innovation was failing to gain traction with young girls. Mattel said it saw a shocking 59 percent drop in profit during its important fourth quarter.

Sales of its Monster High dolls have been a relative bright spot for Mattel, but even that success has a soft underbelly. Monster High, a line of dolls that sport funky fashions and a haunted house-inspired look, appeals to much the same age group as Barbie. And so Monster High sales appear to be cannibalizing sales of Barbie dolls, rather than growing Mattel’s top line.

Another tailwind for Mattel this year was its wide array of toys related to Disney’s smash hit “Frozen,”  but that won’t last much longer. In September, Disney announced it will take the licenses for those toys to Hasbro in 2016. So while Mattel has another year to wring money out of this wildly popular franchise, it is going to have a gaping revenue hole to plug in the not-too-distant future.

Mattel’s gloomy 2014 came even as the broader toy industry saw healthy growth. Toy sales reached $18.08 billion in 2014, a four percent increase over 2013, according to research firm NPD Group. Rival Lego surpassed Mattel for the first time as the world’s largest toymaker as “The Lego Movie” rocketed to success at the box office.

Stockton has said that Mattel’s struggles during his tenure were in part born out of a need to be more innovative, not only in making toys, but in marketing and advertising them. To that end, he established a division within Mattel, dubbed the Toy Box, that was to be the company’s new hub of creativity, a place where workers conceptualize new toys and come up with ways to leverage the entertainment partnerships they already have. It remains to be seen whether the young division can play a role in restoring Mattel’s battered image.

Investors appear unconvinced. The company’s stock, already down more than 20 percent over the last six months, fell another four percent Monday afternoon.