Stoke defender Harry Souttar was sent off as the Potters were held to a dour goalless draw by Preston.
Earlier, Preston's Andrew Hughes went close to breaking the deadlock when his second-half free-kick struck the post.
Potters striker Steven Fletcher found the net soon afterwards after being found by Nick Powell, but the effort was disallowed for offside.
It was an afternoon to forget for Souttar, who missed chances to score before being dismissed.
He headed wide from crosses by Sam Clucas and Tommy Smith.
The visitors defended well and frustrated their opponents, whose play-off hopes faded some time ago.