Berg had supported Manchester United as a boy and manager Alex Ferguson had first wanted to sign Berg for United nine years earlier when he was a teenager, but the move fell through because United could not obtain a work permit. Berg was a regular choice in the Manchester United line-up during the 1997–98 season, but the arrival of Jaap Stam in July 1998 meant he was restricted to just 16 Premier League appearances in 1998–99 as the team won the Treble of the Premier League, the FA Cup and the UEFA Champions League. Berg missed the 1999 FA Cup Final and the 1999 UEFA Champions League Final through injury, but still picked up a medal for both, having been involved in most of the team's matches on the way to the final. With the league title in 1999, Berg became the first player to win the Premier League with two clubs, a feat he would be alone with until 2010, when it was matched by Ashley Cole and Nicolas Anelka. Gael Clichy, Kolo Touré, Carlos Tevez, Robert Huth, N'Golo Kanté and Riyad Mahrez have all since matched the feat as well. Berg regained his place in the side during the 1999–2000 season, when Ronny Johnsen was injured.