Vrsaljko was forced off with just four minutes remaining of Croatia's vital 2-0 World Cup qualifying victory over Ukraine on Monday night (9 October) after appearing to sustain a hamstring problem.
The 25-year-old was eager to allay fears over any fresh injury blow after a win which saw Croatia, who replaced manager Ante Cacic with Zlatko Dalic just two days before that decisive trip to Kiev, secure a play-off spot ahead of their hosts.
"It's not an injury," he told reporters, per Marca. "I just felt a discomfort in my hamstring and I think it was right for the team to bring on a fresher player so that we were not weaker on that side. I couldn't sprint, so I thought it better to come off."
Vrsaljko returned to Madrid on Tuesday and subsequently underwent medical tests to determine the severity of the complaint. In an update released via their official website, Atletico have now confirmed that the player has avoided any serious damage.
However, they insist that he is suffering from muscle fatigue in his right hamstring and will "have to take it easy before being able to train with 100 percent normality". That would presumably make him a real doubt for the meeting with Barcelona.
Vrsaljko has yet to establish himself as a first-team regular under Diego Simeone since joining Atletico from Serie A outfit Sassuolo in a €16m (£14.3m, $18.9m) deal last summer, making just three appearances in 2017-18 to date.
He started the 2-0 victory over Sevilla on 23 September after not featuring for almost a month due to a foot issue and, having been left out of the matchday squad altogether for the last-gasp Champions League defeat to Chelsea. He was introduced as a second-half substitute during the goalless draw at Leganes with Jose Maria Gimenez getting the nod at right-back.
Simeone had already been handed a double boost ahead of Barcelona's first visit to the Wanda Metropolitano, with defenders Filipe Luis and Lucas Hernandez both returning to first-team training on Tuesday morning. However, Los Colchoneros tempered expectations somewhat by insisting that the duo have yet to receive the necessary medical clearance to be able to play in matches.
Atletico currently sit fourth in La Liga after winning four of their opening seven matches, level on points with third-place Valencia and six adrift of Barcelona. After entertaining the latter this weekend, next up for Simeone's side is a lengthy trip to Azerbaijan to face Champions League debutants FK Qarabag in Baku.