Messi, whose future remains unresolved with his contract expiring in June, scored twice in that win at the Mestalla to take his tally in the league this season to 28.
The Barca captain has improved in the second half of the campaign after trying to leave the club last summer and his goals have helped cut the gap on Atletico from 13 points to two.
He gathered the squad at his property in Castelldefels, a seaside town outside of Barcelona, after Monday’s training session ahead of what could prove a defining week in the title race.
The players’ partners were also invited to the event, which a source told ESPN was to to bring the squad together in a different environment before the Atletico game.
With no game in midweek, coach Ronald Koeman has given the players Tuesday off. They don’t train again until Wednesday evening.
They play Diego Simeone’s side at Camp Nou on Saturday knowing they will leapfrog them with a victory, although their hopes of winning the league also depend on Real Madrid dropping points.
Barca and Madrid both have 74 points but Los Blancos will win the league if the two sides finish level courtesy of their superior head-to-head record.
Despite needing Madrid to drop points, president Joan Laporta has expressed his belief that four wins will guarantee Barca the title.
“I said before the weekend that if we win all five remaining games, we’re convinced we will win the league,” Laporta said at the airport in Valencia on Sunday. “Now it’s four wins to win the title.”