British hopeful Dan Evans scooped the biggest ATP Tour title of his career at the Citi Open in Washington on Sunday.
Andy Murray came up just short in a three-hour marathon against world number nine Taylor Fritz in the last 16 of the Citi Open.
Alexander Zverev won the Hamburg Open while Taylor Fritz was crowned Atlanta Open champion in Sunday's ATP action.
Former world number four Kei Nishikori won his first ATP Tour match in 19 months at the Atlanta Open on Tuesday.
Former US Open winner Marin Cilic is set to make a long-awaited return to the ATP Tour at his home event in Umag, Croatia, this week.
Tennis Canada announced that Novak Djokovic has withdrawn from next month's National Bank Open in Toronto due to fatigue.