In the past, Southgate has cracked the whip when players have stepped out of line, but Maddison's inclusion reflects the difficulty the England manager has in finding a creative talent to complete his preparations for Euro 2020.
Victory over Montenegro at Wembley would seal qualification in what will be England's 1,000th worldwide.
Callum Hudson-Odoi and Alex Oxlade-Chamberlain have been recalled to the England squad, but there is no place for Jack Grealish.
His Blues team-mates Ross Barkley, Mason Mount, Tammy Abraham and Fikayo Tomori have also been included.
Leceister City midfielder James Maddison is named in a third straight squad, but he has yet to feature, having dropped out of the previous two with injury and illness.
The Chelsea youngster was called up to the England Under-21 squad last month following his return from an Achilles injury.
England host Montenegro on November 14 and travel to Kosovo on November 17.