Berlin: Pep Guardiola's former team meets his current employers in a friendly on Wednesday, as European champions Bayern Munich host Barcelona with relations strained between the Spaniard and his ex-club.
On Tuesday, Barcelona named former Paraguay manager and Argentina midfielder Gerardo Martino as head coach to replace Tito Vilanova, who resigned Friday as he battles against cancer.
After Guardiola won 14 titles between 2008 and 2012 at Barcelona, the pre-season run-out has added spice given recent events which have strained relations between the two European powerhouses.
Guardiola took charge of Bayern last month amid great fanfare, after the Bavarians lured the 42-year-old to Munich following his year's sabbatical in New York.
Guardiola has already poached Spain Under-21 captain Thiago Alcantara from Barcelona to bolster his star-studded midfield which includes Holland's Arjen Robben and France winger Franck Ribery.
But Guardiola stirred up bad blood with his former bosses earlier this month when he accused the Barcelona board of trying to "damage" him.
Guardiola lashed out in a press conference, making allegations against the board, which were later refuted, that he had snubbed Vilanova while he was being treated for cancer in New York.
"I will never forget that they used Tito's illness to cause me damage, because it's a lie that I never saw him in New York," he said.
With relations strained off the field, there is plenty of spice on it, although both teams are likely to name weakened teams.
Bayern's Germany stars Bastian Schweinsteiger and Mario Goetze are both recovering from injury, while neither team is expected to have their Confederations Cup stars in action.
Both Barcelona's new Brazil star Neymar and Spain's Carles Puyol, who is working his way back to fitness after knee surgery in March, are expected to sit it out.
Senior stars Javier Mascherano, Adriano Correia, Alex Song and Alexis Sanchez are likely to feature among a host of reserves, while Argentinian superstar Lionel Messi is set to play some part.
Barcelona have something to prove against Bayern having been humbled 7-0 on aggregate in last season's Champions League finals when the Germans backed up a 4-0 win in Munich with a 3-0 rout at the Camp Nou.
Having already chalked up wins over Bundesliga opposition Hamburg and Borussia Moenchengladbach in a pre-season tournament over the weekend, the Barcelona friendly is a big test for Guardiola's new-look Bayern.
He has introduced a 4-1-4-1 system, from the 4-2-3-1 formation which won last season's treble, and switched Germany captain Philipp Lahm from right-back into midfield with France winger Franck Ribery up front.
The game's kick-off time has been brought forward to 1830 local time (1630 GMT) to allow home-team fans to watch Germany's women in the semi-final of the 2013 European Championships.