Graeme McDowell will not return home to play in the Irish Open as defending a PGA Tour title at the same time "is the best option for me at this time".
The absence of the former US Open winner is a blow for the Galgorm Castle tournament on 24-27 September, which was moved from May because of Covid-19.
"I have never failed to attend this great event for 18 years," he said.
"Due to the necessary changes to the event, travel and scheduling, I am choosing not to play this year."
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This year's Irish Open was originally scheduled for Mount Juliet in Kilkenny but it fell victim to the coronavirus pandemic.
The Irish government's Covid-19 restrictions led to the Galgorm Castle course venue being confirmed as the new host.
Open champion Shane Lowry, who won the tournament as an amateur in 2009, provided a boost on Tuesday by confirming his participation in Ballymena.
McDowell has made the "very difficult decision" not to join fellow Irishman Lowry in the event as he defends the Corales Punta Cana Resort and Club Championship title in the Dominican Republic.
"Defending a title is something special and an honour I have tried to take seriously all my career," added the Portrush man, who also apologised to the tournament sponsors for his absence.
"Under normal circumstances defending this event would not take priority over playing my home Open, but the unprecedented circumstances make this a better option at this time."
"We will hopefully be back in 2021, with the event at full strength, surrounded by great Irish fans, assuming we can put the issues caused by Covid behind us."