Emma Raducanu blamed fatigue after suffering a straight-sets defeat to Argentinian qualifier Maria Lourdes Carle in the first round of the Madrid Open.
Emma Raducanu's progress in the Stuttgart Open was halted in straight sets by world number one Iga Swiatek.
Angelique Kerber, the 2015 and 2016 Porsche Tennis Grand Prix winner, was defeated 6-2 6-1 by Emma Raducanu in Stuttgart on Wednesday.
Emma Raducanu produced a brilliant comeback to stun France's Caroline Garcia and draw Great Britain level at 1-1 in the Billie Jean King Cup qualifier in Le Portel.
Emma Raducanu's representatives have assured that the back injury, which forced her withdrawal from the Miami Open, is "nothing serious".
Emma Raducanu's injury problems have resurfaced, causing her to withdraw from the Miami Open ahead of her first-round match.