The cause of Manchester United defender Victor Lindelof's breathing problems during the match against Norwich City is not believed to be linked to the club's Covid-19 outbreak. Lindelof, 27, was substituted in the 74th minute if the <a href="https://www.thenationalnews.com/sport/football/2021/12/12/norwich-v-manchester-united-player-ratings-krul-7-pukki-6-ronaldo-5-fred-7/" target="_blank">1-0 win at Carrow Road</a> after struggling to catch his breath. United interim manager Ralf Rangnick said after the match the Sweden defender also had a higher heart rate than normal, prompting the decision to replace him. In a statement released on Tuesday, United said: “Victor is currently undergoing a series of precautionary investigations. He has recovered well from the episode he experienced in the match against Norwich. “All indications are that this is not linked to any Covid outbreak within the club.” Lindelof’s wife Maja has revealed that her husband has been given a heart monitor as club doctors try to understand the cause of the problems he suffered. In a blog entry posted on Monday, she wrote: “It was a scary match to watch and Victor was very concerned afterwards. Yesterday he did a lot of tests and has a heart monitor on for two days to make sure everything is OK. “Everything seems to be OK as luck would have it and we are waiting for answers to the last tests that will end tomorrow.” United’s Premier League match away to Brentford, scheduled for Tuesday night, was <a href="https://www.thenationalnews.com/sport/football/2021/12/14/brentford-v-manchester-united-postponed-after-covid-outbreak-at-carrington-complex/" target="_blank">postponed after a number of positive Covid-19 tests</a> among players and staff led to the closure of their Carrington training complex on Monday. Meanwhile, Premier League players and club staff will have to take a lateral flow in order to get into training grounds as part of new measures agreed on Tuesday. It was confirmed on Monday that there had been 42 positive Covid results over the previous week, with outbreaks at <a href="https://www.thenationalnews.com/sport/football/2021/12/10/tottenhams-match-against-brighton-postponed-after-covid-outbreak/" target="_blank">Tottenham Hotspur</a> and United causing two games to be called off in three days. As well as the daily tests to get into training grounds, players and staff will now have a PCR test twice a week — which was the case last season until it was changed to lateral flows in the summer.