According to the BBC, Onana, who had a hamstring injury during training, will miss the club's preseason game in the United States, but will still go to the United States with the team.
29-year-old Cameroon international responded well to initial treatment and will still go to the United States to compete in three preseason games in late July, but his time will be spent on recovery.
This means that in the preseason, Baindel will likely become Amorin's first choice goalkeeper. His future at Manchester United was questioned before, because despite Onana's decline in form, Baindel still failed to get a starting chance in the UEFA Europa League final in May.
It is unclear whether Onana's injury will force United to find a new goalkeeper in the transfer market, and rumors have been rumored to consider other options at the end of last season.
On July 19, Manchester United will play against Leeds United in a friendly match.