UPDATE: Gary Johnson has travelled to Northern Ireland to take over Lee Johnston's rides on the East Coast BMW and Triumph machines.
Lee Johnston has been ruled out of the MCE Ulster Grand Prix after suffering a broken collarbone on the opening day of practice.
Johnston came off his 250cc Honda at the hairpin in wet and miserable conditions at the Dundrod course.
He claimed the man of the meeting award last year following a superb hat-trick, including wins in both Supersport races and the Superstock event.
Johnston had battled back to fitness after a crash at the Scarborough Spring Cup meeting left him nursing injuries at the North West 200 and Isle of Man TT.
Poor weather and an oil spill led to long delays during the first practice sessions for the Ulster Grand Prix on Wednesday.