Europe’s biggest clubs return for Matchday 4 of the UEFA Champions League, and the match-ups couldn’t be bigger. Markus and Jan Åge Fjørtoft break down all four fixtures: Bayern Munich's historic run as they face defending champions PSG, Kovač’s disciplined Dortmund take on Manchester City in another Erling Haaland reunion, Napoli and Frankfurt meet in a high-stakes clash, and Mourinho’s Benfica host Hjulmand’s Leverkusen in search of their first win.