HBO chief technology officer Otto Berkes is exiting after the premium cable network decided to enlist Major League Baseball Advanced Media to build its over-the-top streaming service instead of developing it inhouse.

This fall, HBO said it would launch a standalone OTT service in 2015. It has been aiming for an April debut — timed for the fifth season of “Game of Thrones” — although that is subject to change, according to a source familiar with the plans.

HBO’s move to enlist MLBAM to build its OTT infrastructure and the April target launch date were previously reported by Fortune.

Berkes announced his resignation Tuesday in a memo to HBO staff, a copy of which was obtained by Variety.

“Recently HBO’s management decided to partner with a third party to assist HBO in bringing our OTT service to market in 2015,” Berkes wrote. “This is a change in direction from what I planned with HBO and the approach will not utilize my overall capabilities. Therefore, I feel that this is the right time for me to move on from HBO so that I am able to fully pursue my passion building world-class technology teams, products and businesses.”

Berkes, one of the original creators of Microsoft’s Xbox, joined HBO in 2011 as senior VP of digital products, leading development of HBO Go and the cabler’s other consumer technologies. In 2012, he was promoted to CTO, replacing longtime technology chief Bob Zitter.

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HBO decided to go with MLBAM based on its past expertise in streaming media. MLBAM, in addition to operating the MLB.tv subscription streaming service for out-of-market baseball games, also powers the streaming infrastructure of WWE Network and has worked with CBS Sportsline’s March Madness on Demand service and ESPN’s WatchESPN service.

Earlier this year, the HBO Go service suffered critical outages during the finale of “True Detective” and the “Game of Thrones” season four premiere.

Under Berkes, HBO had been developing a streaming-video platform with the code-name “Maui” designed for the OTT service. But the Maui system was a “less-than-perfect solution” and the project was shut down, according to a memo sent to team members by Mark Thomas, senior VP of technology program management, and Drew Angeloff, senior VP of digital products. The memo was previously published by Fortune.

“This was not a judgment of the team’s work quality or deliverables but rather a bet that an existing streaming service could deliver the needed product faster and at lower risk than Maui,” Thomas and Angeloff wrote in the memo.

The execs added that “Maui’s timeframe caused us to make concessions both in scope and culture. We look forward to returning to teams defining scope, and consumer experiences, without forced top-down scheduling.” Meanwhile, a “large portion” of Maui can be repurposed for HBO Go, according to the memo.

In a statement, an HBO rep said that the Maui project “was one of several options on the table to accomplish the undertaking of offering a standalone HBO product for next year. It is not uncommon to use outside resources in this type of project. This in no way impacts our plans and we’re excited to bring an over-the-top HBO product to market next year.”