With Bayern Munich wobbling, the clash between Borussia Dortmund and RB Leipzig on Friday, the two sides most likely to snatch the Bavarians' crown, comes at a pivotal time.Despite Union Berlin's stunning run, as well as brave challenges from Eintracht Frankfurt and Freiburg this season, Dortmund and RB Leipzig remain the two sides with the best chance of stopping Bayern's quest for an 11th straight title.In the six seasons since Leipzig's promotion for the 2016-17 season, the two have regularly wrestled for the runners-up spot, with Dortmund finishing second three times, Leipzig twice and Schalke once, in 2017-18.While Dortmund's season appeared to be a write-off after consecutive losses left them nine points off Bayern before the winter break, a run of seven consecutive league victories -- plus wins in the Champions League and German Cup -- have revived their season.Bayern's struggles in 2023, with just three wins from seven league matches, means Dortmund have closed the gap and sit alongside the Bavarians atop the table.Dortmund and Union's form -- and Bayern's struggles -- have allowed Leipzig to quietly plot their title challenge out of the spotlight.Leipzig have 37 points in 17 games since former Dortmund manager Marco Rose took over in early September, more than any other Bundesliga team.Rose's Leipzig tenure was kick-started by a dominant 3-0 home win over his former side, Dortmund's biggest loss in all competitions this season.RB now sit in fourth place, four points behind Bayern and Dortmund, with 12 matches remaining this season.Leipzig have won their last three meetings with Dortmund, including a 4-1 away thrashing in 2021-22.Prior to that, Dortmund had gone unbeaten in eight against Leipzig, a run of six