Lionel Messi was taken to hospital after suffering an injury scare on Friday as Argentina defeated Honduras 1-0 in their only warm-up game before next month's Copa America Centenario in the United States.
A first-half goal from in-form Napoli striker Gonzalo Higuain settled a low-key encounter in San Juan, with two-time world champions Argentina dominating possession and shots.
But the result was overshadowed by an alarming incident involving Messi midway through the second half that forced the Barcelona superstar to leave the field clutching his lower back in pain.
The five-time FIFA World Player of the Year appeared to be hurt after a heavy aerial collision with an opposing player in the 59th minute.
Messi grimaced and rubbed his lower back after the challenge and required treatment on the field for several minutes before he was swiftly substituted by Ever Banega.
Messi was taken to hospital to assess the nature of the injury, the Argentina Football Association said in a statement.
"Messi suffered trauma to his lower back on the left side and ribcage in the same area. He is being examined in a local hospital for a more thorough diagnosis," the statement said.
He had suffered a "nasty blow to the lower back," Argentina coach Gerardo Martino said.
"It's too early for me to say anything more at this stage," Martino told a post-match news conference.
However, any injury to Messi will be a huge blow to Argentina as they prepare for their opening Copa America Centenario match against Chile in California on June 6.
Messi is crucial to Argentina's hopes of winning a first major tournament for 23 years, and was player of the tournament at last year's Copa America and the 2014 World Cup.
The 28-year-old Argentina captain missed two months of last season's club campaign for Barcelona after suffering a serious knee injury in September.
Messi is also due to return to Spain this weekend to attend a hearing in his tax fraud trial, before then jetting off to California to reunite with the Argentina squad.
Earlier in Friday's match, Higuain's goal in the 31st minute had settled the encounter for the hosts.
The striker produced a sublime Cruyff turn to wrongfoot defender Maynor Figueroa before lifting a delicate finish over goalkeeper Donis Escober.
Argentina had earlier threatened the Honduras goal when Messi played in Angel Di Maria only for the Paris Saint-Germain forward to shoot over the bar.
Manchester City defender Nicolas Otamendi also went close on 28 minutes, volleying just wide from Di Maria's corner.