Freddie Sears volleyed wide after a corner was half-punched clear by Foster before a Larsson clearance hit Matthew Upson - playing at left-back - and forced Foster into a fine reaction save at his near post.
The Ajax keeper had another nervous moment at the start of the second half when he beat Edinson Cavani to a through ball but failed to make a proper clearance and Van Bronkhorst had to clear Alvaro Pereira's curling shot off the line.