The British driver has been unable to match his 19-year-old Mercedes team-mate in the grid’s dominant car.
The world number two laboured to an eight-over finish at last week’s St Jude Championship.
Steve Borthwick’s team lifted their total of yellow cards for 2026 to 15 in eight Tests.
The three-year-old gelding won the £150,000 Moet and Chandon International at Ascot last month.