Reyna, 17, was due to start the first match following the return from the coronavirus stoppage, but was injured in the warm-up for the clash at Schalke, while illness ruled him out of the midweek clash with Mainz.
Dortmund manager Lucien Favre was full of praise for the U.S. teen ahead of the clash with Mainz.
"He's only 17 but he's a huge talent," Favre had said. "He understands football, makes the right runs, defends properly. It's fantastic what he does."
This is Reyna's 17th appearance this season, having made his debut alongside Haaland in the 5-3 victory over Augsburg in January.
Despite their shock midweek clash with Mainz, second-place Dortmund were assured of Champions League qualification for next season ahead of their trip to Leipzig.
ESPN's Germany correspondent Stephan Uersfeld contributed to this report.