Messi scored Barcelonas second goal against Sevilla following Philippe Coutinhos 2nd-minute opener but the Argentinian icon was forced off in the 26th minute at the Nou Camp.
The 31-year-old landed awkwardly on his arm and a physio applied strapping before Ousmane Dembele came on as a replacement.
Tests carried out on the first team player Leo Messi have confirmed that he has a fracture of the radial bone in his right arm, Barcelonas official account tweeted after their 4-2 victory.
He will be out for approximately three weeks.
[INJURY NEWS] Tests carried out on the first team player Leo Messi have confirmed that he has a fracture of the radial bone in his right arm. He will be out for approximately three weeks. #FuerzaLeo pic.twitter.com/kpNcspnfqo
— FC Barcelona (@FCBarcelona) October 20, 2018
Barcelona, sitting at the top of the table, are now four points above fifth-placed Real Madrid ahead of their showdown next weekend.
Julen Lopetegui is under intense pressure at the Bernabeu their third defeat on the bounce to Levante.
Asked about rumours that Lopetegui could be sacked, Sergio Ramos replied: I always said that manager changes are never good for anyone. Its a bit of an advantage. Calm must be kept.
We do not make decisions about who has to be a coach.
Julen has the support of all his players and together we will see how to turn this around.