Everton boosted their chances of playing in Europe next season with a 1-0 home win over Southampton on Monday night.
The Toffees, fresh from a 2-0 win over rivals Liverpool, put in an impressive display against the Saints, who are winless in their last seven games.
Richarlison gave the Toffees the opener after just nine minutes, and it proved the all-important strike.
The match got off to a slow start, but it did not take long for the moment of the match to arrive.
Richarlison took Sigurdsson's pass, rounded Forster, and calmly tucked his shot away from the acute angle to give the hosts the lead.
The Toffees then looked to double their lead in the 15th minute from a set-piece as Sigurdsson's cross from the right was headed towards goal by Richarlison but Forster got down to make a good save.
Both teams struggled to keep hold of possession as the match progressed, even though Everton looked sharper.
They thought they had doubled their lead when Michael Keane headed home from close range following a well-worked free-kick, but his effort was ruled out for offside.
Everton kept threatening in the second period with Digne coming close in the 58th minute, but Ward-Prowse managed to clear the danger by heading off his line.
Vestergaard then made a crucial intervention just after the hour mark to deny Holgate, who was about to score from a Sigurdsson free-kick.
Carlo Ancelotti's side enjoyed good possession in the last half-an-hour, but could not add to Richarlison's goal as they picked a key win, their second on the row.
The three points pulled them level with Liverpool on 43, but have an advantage over their rivals with a game at hand.