Barca blitzed fellow Catalan side Girona 6-1 on Saturday to go 10 points clear, but Atletico cut that lead back to seven the next day by hammering Sevilla 5-2 away from home.
Sunday's clash could breathe new life into the title race or leave clear daylight between Barca and the rest, though the Catalans must first get past Las Palmas on Thursday.
The Canary Islands team are fighting relegation but making steady progress under coach Paco Jemez.
Jemez, who has a reputation for producing attacking sides, has transformed his charges from a team that routinely leaked goals into one that has kept three clean sheets in their last four games.
Barca will be without defenders Nelson Semedo and Jordi Alba due to injury, while Gerard Pique could be rested after coming off against Girona showing signs of discomfort in his knee.
Barca will also have one day less to recover than Atletico ahead of Sunday's game at the Nou Camp, as well as contending with a three-and-a-half hour flight back to the mainland.
Atletico exploited Sevilla's defensive weaknesses to devastating effect on Sunday as Antoine Griezmann scored his first hat-trick of the season but his side have rarely found life easy against Leganes, who they host at the Wanda Metropolitano stadium on Wednesday.
Asier Garitano's team have held Atletico to goalless draws in two of their three games in the top flight.
"Leganes ...have an incredible defence and we will have to be at our very best to beat them," said Atletico coach Diego Simeone, whose side have won their last seven games in all competitions.
Third-placed Real Madrid also enjoyed a big win at the weekend, thrashing Alaves 4-0, and on Tuesday face one of their most accommodating opponents in Espanyol, having bested the Catalan side in their last 10 league encounters.
(Reporting by Richard Martin; editing by John Stonestreet)
