Dortmund: Borussia Dortmund teenager Erling Haaland followed up his debut hat-trick by scoring two more goals, again off the bench, in a 5-1 demolition of Cologne in the Bundesliga on Friday.
Fellow 19-year-old Jadon Sancho was also on target with his 11th Bundesliga goal of the season and his eighth in his last eight outings as Dortmund outclassed the hapless Billy Goats.
Raphael Guerreiro and Marco Reus scored first-half goals as the third-placed hosts cut the gap to RB Leipzig to four points before the leaders visit Eintracht Frankfurt on Saturday.
Haaland, the first player ever to score five goals in his first two Bundesliga appearances, has come on in the second half both times and spent a total of 59 minutes on the pitch.
He scored 28 goals in 22 games for Austrian side Salzburg in the first half of the season before joining Dortmund.
Both first-half goals came from long passes upfield from defender Mats Hummels, who also saw a header hit the bar.
The first goal, in the first minute, ended with Sancho crossing from the right for Guerreiro to score with a first-time shot which keeper Timo Horn got a foot to but could not stop.
For the second, Reus peeled away from the Cologne defence to latch onto Hummels' raking pass and steer the ball through Horn's legs. The goal was initially ruled out for offside but awarded after a VAR review.
In between, Dortmund were awarded a penalty for a foul on Achraf Hakimi by Sebastiaan Bornauw but, after a VAR review, the referee ruled it was outside the area and gave a free kick.
Sancho increased the lead three minutes after the re-start with a clinical finish from a Reus pass before Mark Uth pulled one back with a superb volley from a tight angle.
Haaland, who entered the fray in the 65th minute, got a poacher's goal when he turned in a rebound for the fourth in the 77th.
Ten minutes later, the prolific Norwegian raced onto a through ball, slipped past Horn and rolled the ball into the net from the narrowest of angles before milking the applause from the Suedtribune.
Champions Bayern Munich, who are level on 36 points with Dortmund, host Schalke in Saturday's late game.