Rapid put Esbjerg to a real test with a nip-and-tuck first half, but the Danish side never caved in and delivered a better second-half performance.
Esbjerg began brightly, but the Romanian side kept it tight mostly thanks to Denisa Sandru's outstanding reflexes, and her 11 saves at halftime at 48 per cent save efficiency did not let Esbjerg break free.
However, when her string of saves came to a halt, Henny Reistad spurned the Danes on to a tight win (28-26) in the Romanian capital.
Nykøbing remain at the bottom of the group after a tough loss (27-29) after failing to find their rhythm, converting only 28 per cent of their shots in the first half, while goalkeeper Gabriela Moreschi and right back Monika Kobylinska proved to be instrumental in CSM’s dominance.
Bucuresi's biggest lead in the game was by eight during the second half, but the Danes closed the gap to 24:25 with eight minutes remaining. However, CSM survived the scare and held their ground to win.