Jordi Alba and Sergio Busquets paid a visit to former Barcelona team-mate Marc Barta as he continues his recovery from a broken wrist suffered during last week's attack on Borussia Dortmund's team bus.
A window on the bus shattered and Bartra also had debris removed from his hand, while the match was pushed back a day and Monaco claimed a 3-2 first-leg advantage.
Alba posted a picture of the trio on Instagram and said: "What a joy to see you and to share laughs together, my friend."
In an Instagram post of his own last Friday, Bartra described the ordeal of the attack as "the longest 15 minutes of my life".
Dortmund got back to winning ways by beating Eintracht Frankfurt 3-1 on Saturday, where Bartra's team-mates paid tribute to him by holding up his playing shirt and chanting his name with the crowd after the Bundesliga match.
Busquets and Alba face a critical week in Barcelona's season, with Sunday's Clasico trip to Real Madrid coming after Juventus' visit to Camp Nou, where Luis Enrique's men must try to summon further Champions League heroics as they tackle a 3-0 deficit.