The 24-year-old is back in training with Chelsea after the USA’s World Cup campaign ended with a defeat to Netherlands in the last 16.
Ahead of the tournament in Qatar, Pulisic had struggled to secure regular playing time at Chelsea, starting just three games in the Premier League before the domestic season was halted.
Reports have claimed that Pulisic could be offered a way out of Chelsea in January with Manchester United interested in signing the winger on an initial loan deal.
Arsenal and Newcastle United have also been linked with a move for Pulisic, although it has now emerged that the Gunners are prioritising a deal for Shakhtar Donetsk winger Mykhaylo Mudryk.
Johnson, though, has urged Pulisic to stay and fight for his place at Chelsea under head coach Graham Potter – who replaced Thomas Tuchel in September.
‘I want Chelsea to keep Christian Pulisic, he shouldn’t leave for Manchester United,’ Johnson told Midnite.
‘I have defended him for a long time and said he has so much potential, but now he needs to prove it.
‘He still has loads to give, give him one more serious season, but if we’re having the same conversations this time next year, he has to go.’
Johnson also feels that Chelsea should consider bringing in free agent Cristiano Ronaldo on a six-month deal until the end of the season following his exit from United.
‘I would take Cristiano Ronaldo at Chelsea for six months, absolutely,’ he added.
‘Ronaldo has been the second or third-best player we’ve seen in our generation.
‘If Ronaldo wants to be back in the same rank as Kylian Mbappe, Lionel Messi or Neymar, he needs to improve.’