Andy Murray has withdrawn from this week's ATP event in Cologne due to a lingering pelvic problem.
The British former world number one first became aware of the issue at last month's US Open.
A scan conducted after his return to the UK revealed tendonitis of the psoas: the muscle which joins the lower back to the top of the leg.
Murray had been due to face the Serbian wildcard Danilo Petrovic in the first round.
Speaking before last week's opening round defeat to Fernando Verdasco, in the first of two back-to-back tournaments in Cologne, Murray stressed the importance of getting matches under his belt.