The three points saw Leipzig claim their first victory after going the entire month of March without victory in three attempts, losing twice and drawing once since their last victory against FC Koln on the 25th of February.
The resounding performance also saw Leipzig tighten their grip on the second-place finish which will see them qualify for the Champions League.
Back from international duty with his native Guinea,Keita volleyed home the opener after meeting a deflected Emil Forsberg effort to open the scoring in the 12th minute from just inside the area.
Forsberg would soon get himself on the scoresheet as he doubled the lead when his long-range effort took a deflection and found the back of the net.
Sandro Sirigu received his marching orders for a second bookable offence and Willi Orban pounced on the numerical advantage to head Die Bullen’s third from a corner.
Keita grabbed his second of the day in the 80th minute.
The strikes were his fifth and sixth of the campaign and this was the first time the 22-year-old has found the net since last scoring in November 2016.
Congo DR international Wilson Kamavuaka featured from the bench for the Lilies, who have lost all 13 away matches this campaign.