AZ went into the match having won only one of their last six league games while Groningen were fresh from a 5-1 cup thrashing of Vitesse Arnhem in midweek.

The visitors began brightly, with Graziano Pelle and Brett Holman both firing in decent shots, while Goran Lovre volleyed over from the edge of the area at the other end.

AZ were nearly ahead in the 37th minute when Holman's fierce effort struck the bar before eventually being cleared.

Just before the break the visitors threatened again after David Mendes Da Silva was fouled in a dangerous position but his free-kick was narrowly off target.

Thomas Enevoldsen broke through for Groningen at the start of the second half only to run out of steam when faced with keeper Sergio Romero.

The hosts were warming to their task now and Leandro Bacuna set up Gibril Sankoh for a shot that was comfortably saved by Romero.

Enevoldsen went on another run just after the hour mark but again the final product was lacking, and Groningen were made to rue their missed chances when AZ took the lead against the run of play.

With only five minutes of play remaining, Frederik Stenman fouled Stijn Schaars in the right channel and his free-kick was headed in from close range by Lens.

Stenman nearly made up for his indiscretion when he sent Bacuna through but Romero tipped his effort over the bar.