Chelsea midfielder Mason Mount limped off in his side's 4-4 Champions League draw with Ajax and could miss England's final two Euro 2020 qualifiers.
Mount, 20, went off in the 60th minute with an injury to his right ankle.
"They've strapped his ankle and hopefully it's relatively minor," said Chelsea boss Frank Lampard.
Mount has represented his country four times and was expected to be included in Gareth Southgate's squad, which is set to be named on Thursday.
England play Montenegro at Wembley on Thursday, 14 November, then away in Kosovo three days later and the Three Lions will qualify for Euro 2020 with a game to spare with a win in the first of those matches.
The Euro 2020 competition will be held over 12 different countries, with both semi-finals and the final at Wembley.
Chelsea are fourth in the Premier League and are at home against Crystal Palace on Saturday, with a 12:30 GMT kick-off.