Jockey Barry Geraghty will miss next week's Punchestown Festival and faces three months out after breaking his left arm in the Irish Grand National.
Geraghty only returned a fortnight ago after lung and rib injuries forced him to miss last month's Cheltenham Festival.
He was injured on Monday when his mount Minella Foru fell at the eighth fence.
The 37-year-old, retained rider for racehorse owner JP McManus, will have an operation on his arm on Tuesday.
Prior to his fall, Geraghty had landed the Grade Two juveniles' hurdle on Project Bluebook, trained by John Quinn.
After the Irish National, won by Our Duke, Geraghty missed the winning ride on the Joseph O'Brien-trained Slowmotion in the following race and was taken to hospital for X-rays.
Irish Turf Club medical officer Dr Adrian McGoldrick said: "It is the same injury he suffered last year, but on the other side. He is looking at three months out."
Geraghty's injury-plagued 12 months
July 2016 - Out for more than two months after falling from Cernunnos at Market Rasen
February 2017 - Sidelined for five weeks following fall at Kempton; misses Cheltenham Festival
April 2017 - Facing three months out after Fairyhouse injury; misses Punchestown Festival