He scored twice in the early rounds as Ipswich progressed to an attractive quarter final against St Étienne. In the first leg in France Mariner put two away as Ipswich went 4–1 up, and added another as Ipswich completed the task in the second leg. After winning the semi-final, Mariner scored again in the first leg of the final against AZ Alkmaar as Ipswich coasted to a 3–0 lead, ultimately winning the competition 5–4 on aggregate. Weeks later, Greenwood put him back in the England side as the World Cup qualification campaign resumed with a defeat in Switzerland, a vital victory in Hungary and a shock defeat in Norway. It appeared that they might miss out on the World Cup finals for an unthinkable third tournament in a row, but results elsewhere went their way, meaning England only needed to draw with the already qualified Hungary at Wembley in the final game to guarantee qualification. It was Mariner who scored the only goal in a 1–0 win, though he got it after a stumble which saw him score via a deflection rather than an actual shot on goal.