Justin Hayward, who moved to MS&L from Ogilvy PR, is rumoured to be considering an in-house move.
Tech PROs are calling his departure a blow to MS&L, which counts IT consultancy ThoughtWorks and phone start-up Lebara Mobile among its clients.
'He's known as a real digital guru,' said one. Indeed, Hayward announced his departure from MS&L to industry peers on his Twitter feed.
Agency chief executive Stuart Wilson said he would not be replacing Hayward directly.
'Justin was a junior associate,' he said. 'We've been able to fill his role internally. We'll continue to invest in digital.'