London - The Mercedes Formula One team announced top level technical changes on Thursday with engineering director Aldo Costa moving into an advisory role from next season.
The team said in a statement that performance director Mark Ellis would leave his current role and take a sabbatical from mid-2019, with Loic Serra replacing him.
Costa joined Mercedes in 2011 from Ferrari, where he had been technical director, and the Italian has played a key role in the team winning the last four drivers and constructors' world championships.
Mercedes said he now wanted to spend more time with his family in Italy.
Chief Designer John Owen becomes the senior member of the engineering group, under the leadership of technical director James Allison.
"This is a significant moment for our team and a great opportunity," said principal and shareholder Toto Wolff in a statement.
"We have said many times that you cannot freeze a successful organisation; it is a dynamic structure and I am proud that we are able to hand the baton smoothly to the next generation of leaders inside the team."
Mercedes are fighting Ferrari for both titles this season, with the Italian team 20 points clear in the constructors' standings while Sebastian Vettel leads Mercedes' Lewis Hamilton by eight in their battle.