The 'Sex on Fire' hitmakers have been forced to axe two more dates on their Mechanical Bull Tour after the band's drummer suffered broken ribs when a pedestrian jumped in front of their tour bus forcing it to make an emergency stop on August 9.
Nathan wrote on Twitter: ''I'm so bummed 2 have 2 cancel more shows but I need to be fully recovered before I get back. So sorry to the fans & thanks 4 understanding. (sic)''
Nathan and his band mates - brothers Caleb and Jared, and cousin Matthew - were due to perform in Holmdel, New Jersey, on Thursday (28.08.14) and Pittsburgh, Pennsylvania, on Friday (29.08.14).
The 'Wait for Me' group had already postponed numerous shows as Nathan, 35, recovers from his injuries.
He previously said: ''I'm counting down the days until I can get back in the saddle and continue what has been our best American tour so far.''
The band announced news of Nathan's ailments on their Facebook page, writing: ''The band was en route to their hotel after their show in Boston when a pedestrian jumped in front of their tour bus, causing the bus to stop short, injuring Nathan Followill.
''Nathan is being treated for broken ribs, but is doing well.''
'Smalls Change (Meditations Upon Ageing)' arrives in April.
The two awards have made for a great 72nd birthday present for the country music icon.