With Jack Dorsey’s mobile payment startup Square quickly becoming one of Silicon Valley’s rising stars after a high-profile deal with Starbucks (Nasdaq: SBUX) helped attract renewed investor interest and raise the company to a $3.25 billion valuation, many began to wonder how much role, if any, co-founder Jack Dorsey was still playing in the other prominent tech startup he helped found: Twitter.

Turns out, not too much. After a New York Times profile of Twitter CEO Dick Costolo published the first weekend of October asserted how Dorsey’s role in the social media company has declined alongside the rise of Square, the 35-year old entrepreneur confirmed the suspicions on his personal Tumblr page Tuesday morning. Following a hiatus Dorsey took from Twitter in 2011, he says he now only works at the microblogging site on Tuesday afternoons.

The move makes Dorsey the last of Twitter’s three co-founders to retreat from any role in the company’s day-to-day affairs, raising questions about the company’s future direction as it searches for new ways to monetize its core service and potentially pursue a public offering.

In the blog post, Dorsey took issue with the New York Times’ account that his role at Twitter was scaled back “after employees complained that he was difficult to work with and repeatedly changed his mind about product directions."

“In Spring of 2011, Dick asked me to take an operational role overseeing product, design, and brand,” Dorsey wrote. “Our shared goal was to get those organizations back under him as soon as possible, simply because it was the right thing to do for the company. We moved all of my reports back under him in January of this year after leadership was firmly in place.”

Though he admitted that his current position is “not a common arrangement,” he maintained that the schedule at Twitter was part of a plan worked out between him and Costolo that would allow him to “focus on refining our brand and logo,” and help the existing execute team at Twitter establish a “clear direction forward.”

Dorsey claimed that the goal was always to allow him to “ultimately return the majority of my time to Square, where I’m CEO.”

As with his new role at Square, Dorsey’s main asset as a Silicon Valley icon has always laid with his product design. He is credited with first conceiving the idea for Twitter, where he also took over the role as chief executive in 2006 until his co-founder Evan William replaced him at the company’s helm in 2008.

According to the Financial Times, Dorsey was insisting as recently as last November that he was still working full time at both Twitter and Square -- managing all aspects of his new company’s rapid expansion while continuing to refine Twitter’s brand.

In his new role, it sounds like Dorsey will still offer a degree of guidance to Twitter’s product development. The biggest question for the social media start-up now, however, is how it might maintain or expand beyond its initial concept and existing user base, now that all of the co-founders have retreated from the company. ]

In the past year, Twitter has overhauled both its mobile and desktop browser-based applications, redesigned its bird-shaped logo, and sought out a number of high profile media partnerships such as NBC and Nascar. But as other prominent social media companies like Facebook (Nasdaq: FB) struggle to maintain their own public offerings, Twitter faces corresponding scrutiny regarding its prospects for long  term revenue.

“We haven’t talked about this publicly because it’s not what people using Twitter every day care about,” Dorsey said of his relative silence regarding his changed position in his blog post.

“I’m fortunate in life to be a part of two foundational and mission-driven organizations, and I’m always going to fight like hell to make them thrive,” he concluded. “And they are! Now back to our work.”