The Scot landed his fourth European Tour title with victory in last year’s event, which marked the circuit’s restart following a Covid-19 lockdown.
It was his first success in just under four years, but the 40-year-old is not among the Scottish contingent for this week’s 2021 edition back at Diamond Country Club in Atzenbrugg, near Vienna.
“It’s a small back issue which he has been advised to rest up for several weeks rather than play at 70 per cent,” said Mark Ingram, of Warren’s management company, Octagon.
Despite Warren’s absence, hopes are high of another Scottish success, with nine of his compatriots in the field.
Flying the Saltire for the circuit’s return following a short break are David Law, Scott Jamieson, David Drysdale, Grant Forrest, Ewen Ferguson, Liam Johnston, Daniel Young, Craig Howie and Euan Walker.
The field is headed by two-time major champion Martin Kaymer.