* Messi suffers hamstring problem
* Fabregas to have tests on knee ligament
Argentina's Lionel Messi picked up a hamstring injury and Spain's Cesc Fabregas a knee complaint in Barcelona's 4-1 La Liga win at Real Betis on Sunday.
World Player of the Year Messi called for a substitution in the first half after tumbling in a challenge, and was replaced by Andres Iniesta in the 21st minute.
Messi has damaged the hamstring in his left leg and will undergo further tests on Monday, the champions said in a statement on their official Twitter feed.
"Messi's injury isn't in the same leg as in the previous cases," Barca coach Gerardo Martino told a news conference.
"We need to let the medics look at it for a proper analysis."
The Argentina international has suffered a string of muscle problems at the start of this campaign and has struggled to reach his best form to date.
He has been called up by Argentina for international friendlies against Ecuador and Bosnia in the United States over the next two weeks.
Fabregas, who set up the opener for Neymar and scored twice in the second half, was substituted late on and is to have tests on a sore ligament in his right knee, the club said.
"I had a problem with it during the week and it felt sore as the game went on," Fabregas told Spanish broadcaster Canal Plus.
"I preferred to be cautious because I suffered a serious knee injury a few years ago."
The former Arsenal captain has also been called up for international duty with world and European champions Spain for friendlies away to Equatorial Guinea and South Africa.