In The Phantom Menace, Qui-Gon Jinn and Obi-Wan Kenobi engage in a two-on-one battle against Darth Maul. Together, Qui-Gon and Obi-Wan seem evenly matched against Darth Maul, with both sides getting in an occasional punch or kick against the other party.
Darth Maul gains the upper hand by temporarily knocking Obi-Wan out of the fight, causing him to fall several levels beneath himself and Qui-Gon. Then Darth Maul begins to fight in a more defensive manner, giving ground and luring Qui-Gon away from Obi-Wan and towards the laser-walls.
It was pretty clear that Darth Maul outclassed both of the Jedi and intended to kill them separately, presumably because it would be easier. Qui-Gon seemed happy to oblige Darth Maul's wishes and followed him to his death.
Qui-Gon already knew from his encounter with Darth Maul on Tatooine that he was not a match against him one-on-one. Why didn't Qui-Gon stand his ground and wait for Obi-Wan to rejoin him?