By Jamie Spencer Manchester City manager Pep Guardiola joked he was ‘so upset’ with Erling Haaland following Saturday’s 4-0 Premier League win over Southampton because the Norwegian only scored once. Haaland has made a mockery of Premier League defences since arriving in England in the summer, scoring 15 times in just nine games so far – including three hat-tricks – and only drawing a blank once. In all competitions, it is a round 20 goals in 13 matches. Man City 4-0 Southampton: Player ratings – Premier LeagueCity were already 3-0 up before Haaland got in on the act. “I’m so upset with him he…