Mats Hummels will help to remedy a lack of quality that hampered Borussia Dortmund in the Bundesliga last season, according to team-mate Marco Reus.
Experienced defender Hummels returned to Signal Iduna Park for a second spell in June, making a €31 million (£28/$35m) switch from Bayern Munich just three years after leaving Dortmund.
In the years without Hummels, Dortmund finished third, fourth and second in the Bundesliga while Bayern clinched the title each season, but the gap between the two sides was just two points at the end of a tense 2018-19 campaign.