Swans boss Garry Monk gave debuts to new signings Franck Tabanou at left-back and Andre Ayew on the left wing. Kyle Naughton started at right-back with Ashley Williams and Kyle Bartley in the heart of the defence.
Jay Fulton was given the holding role in the middle of the park with Ki Sung-Yueng and Gylfi Sigurdsson just in front. Nathan Dyer started on the right wing with Bafe Gomis as the main striker.
With the heat soaring, Monk was expected to make wholesale changes on the hour for the first friendly of the new season.
Borussia started the brighter as Fabianski was forced into a first-minute save from Marlon Ritter before Nico Elvedi headed wide soon after.
Swansea soon settled though and started to force their way into the game with some patient possession. Kyle Bartley was in determined mood as his crunching tackle on Andre Hahn in the 13th minute earned him the first yellow card of the game.
Swansea found themselves behind a minute later though as Ibraham Traore cut in from the right to fire a low shot beyond Fabianski and into the far corner.
Monk’s men kept their heads though and went on to dominate the possession for the rest of the half as Bartley met a Gylfi Sigurdsson corner with a downward header that bounced just wide.
Franck Tabanou, who was impressing down the left with some driving runs, fired a fierce shot wide from the edge of the area with 21 minutes gone before both sides took a well deserved drinks break.
When play resumed, Swansea continued on the front foot as Bafe Gomis headed a Sigurdsson corner inches the wrong side of the upright, before the striker just failed to beat goalkeeper Tobias Sippel to Elvedi’s sliced clearance after good work down the left from Tabanou and Andre Ayew.
Swansea couldn’t grab a deserved equaliser however as the referee brought the first-half to a close.