Task: Question Generation
Input (English): Neville Southall holds the record for the most Everton appearances, having played 751 first-team matches between 1981 and 1997, and previously held the record for the most league clean sheets during a season (15). During the 2008–09 season, this record was beaten by American goalkeeper Tim Howard (17). The late centre half and former captain Brian Labone comes second, having played 534 times. The longest serving player is Goalkeeper Ted Sagar who played for 23 years between 1929 and 1953, both sides of the Second World War, making a total of 495 appearances. The club's top goalscorer, with 383 goals in all competitions, is Dixie Dean; the second-highest goalscorer is Graeme Sharp with 159. Dean still holds the English national record of most goals in a season, with 60.
Output (English): Who currently holds the record for the most league clean sheets during a season?