In a playing career spent mostly with
Blackpool, Mortensen scored 197 league goals in 317 games. Mortensen holds the record of scoring in the most consecutive league matches, with 15. Another record he still holds today is that he scored in twelve consecutive rounds of the
FA Cup, including the defeat in the
1948 FA Cup Final. Blackpool were back at
Wembley for the
1951 FA Cup final. Mortensen had scored five goals during the competition, but could not add to his tally as Blackpool suffered disappointment again. A second-half brace from
Jackie Milburn secured a 2–0 win for
Newcastle United. It was third time lucky for Mortensen and Blackpool as they reached their third final in five years in the
1952–53 season. Mortensen wrote himself into the record books, although the final is commonly referred to as the "Matthews Final". A 2–1 victory against Tottenham took them to their third Wembley final, with
Bolton Wanderers their opponents.
Nat Lofthouse gave Bolton a second-minute lead, before a Mortensen shot was deflected in for the equaliser. Bolton eventually led 3–1, before Matthews set up Mortensen who made it 3–2. With two minutes, remaining Mortensen scored a twenty-yard free kick to bring the scores level at 3–3, becoming the first player to score a hat-trick in a FA Cup final at Wembley. In injury time,
Bill Perry converted a Matthews cross to seal a 4–3 win for Blackpool. Mortensen's hat-trick became a fact retrospectively: his first goal was widely considered an own goal by
Harold Hassell at the time.
Kenneth Wolstenholme, the BBC commentator, attributed the goal to Hassell, as did the Sunday newspapers the following morning. In the book
The Great English Final, author David Tossell states that only since the publication of the FA Yearbook two months later, which awarded Mortensen with all three goals, that the hat-trick became accepted as fact. In the
Charity Shield match at
Highbury against
Arsenal, Mortensen put the FA Cup winners ahead. However,
Tommy Lawton, and a brace from
Doug Lishman, resulted in a 3–1 for Arsenal. The
1950–51 league season saw Mortensen break the record of scoring in the most consecutive matches, a record set by Irishman
Jimmy Dunne twenty years earlier. Although missing two games through injury during the span, Mortensen scored in 15-consecutive matches before a blank, but scored again for 16 goals in 17 matches. He scored 25 goals in 22 games from December as he finished that season with 30 league goals. He was top scorer every season during his time at the club. He started his tenth season with the club before being transferred to Second Division
Hull City. Despite the announcement, he went on to play for
non-League clubs
Bath City and
Lancaster City. ==International career==