Marcus Rashford has described his injury as a "slight niggle" and insists the problem is nothing to be concerned about.
On Tuesday, Southgate confirmed Rashford had picked up a knock but the 20-year-old posted on social media to calm fears over any long-term issues.
"Thanks for the messages I've been getting. Picked up a slight niggle but nothing to worry about #ThreeLions," Rashford wrote.
Rashford scored 13 goals in all competitions for United in 2017-18, fighting for a starting role along with Alexis Sanchez and Anthony Martial.
Following their opener against Tunisia, England face Panama on June 24 and Belgium on June 28.