Having overcome ankle and shoulder injuries over the course of the summer, Nortje made his international debut in March this year and subsequently won selection in South Africa's World Cup squad. Nortje, however, fractured his right thumb during a recent South Africa nets session, and it has now been confirmed that he would need six to eight weeks to make a full recovery.
"Anrich sustained a fracture to his right thumb during a net session in Port Elizabeth on Monday," South Africa team manager Mohammed Moosajee said. "He immediately consulted a hand surgeon and underwent surgery to stabilise the joint and will unfortunately be sidelined for up to eight weeks. This makes him unavailable for the upcoming ICC Men's Cricket World Cup.
"It is an unfortunate and freakish injury, especially because he had made a successful recovery from the shoulder injury he sustained during the series against Sri Lanka. He has had a few injury setbacks in the last year but knowing Anrich's character, he will be motivated to come back stronger. We wish him a speedy recovery."
Allrounder Morris, 32, has been called up to replace Nortje in the 15-man squad, with South Africa's opening game against England just over three weeks away. Morris has not played an ODI in more than a year, but was part of the T20I squad that battered Sri Lanka at home in March. Morris is currently in action with Delhi Capitals in the IPL, for whom he has taken 13 wickets in nine games this season.
"Chris has always been in our plans and is our next best option with the ball," national selection panel convener Linda Zondi said. "He has the pace and death-bowling skills which will be vital in the UK, and also gives us that depth as a deadly finisher with the bat. We have had concerns around his injuries and workload capabilities but this is an opportunity for him to make a mark on the biggest stage.
"It is unfortunate what has happened to Anrich, he is a talented player with exciting potential," added Zondi. "We wish him well on his road to recovery and have no doubt that he will bounce back to fulfil his potential."
South Africa have been dealing with multiple injuries in the lead up to the World Cup, with Kagiso Rabada and Dale Steyn's IPL stints cut short by back and shoulder problems, respectively. While Rabada has said that his premature return to South Africa was "precautionary", both he and Steyn are both still being assessed by the South African medical team. Rabada has a history of back trouble, having picked up a stress fracture last year, while Steyn's flare-up was in the same shoulder that he seriously injured in Australia in 2016.
Left-arm wristspinner Tabraiz Shamsi had missed South Africa's domestic T20 competition in order to recover from a stiff back too, while JP Duminy was out of action for most of the summer following shoulder surgery. Both Shamsi and Duminy have fully recovered, though.
"Admittedly, the injuries ahead of the tournament have been frustrating but I continue to have confidence that the players we have selected will make the country proud," Zondi added.
Squad (updated): Faf du Plessis (capt), JP Duminy, David Miller, Dale Steyn, Andile Phehlukwayo, Imran Tahir, Kagiso Rabada, Dwaine Pretorius, Quinton de Kock (wk), Chris Morris, Lungi Ngidi, Aiden Markram, Rassie van der Dussen, Hashim Amla, Tabraiz Shamsi
Liam Brickhill is ESPNcricinfo's South Africa correspondent