The Danes, for whom Henrik Dalsgaard has also been called up, host Faroe Islands in a friendly on Wednesday at the MCH Arena, Herning, home of FC Midtjylland, kick-off 5pm UK time, before a pair of Nations League A2 matches.
The Danes head to Reykjavík to take on Iceland on Sunday, 11 October, kick-off 7.45pm, before a game at Wembley against England 72 hours later.
Denmark opened their League A campaign with a 2-0 defeat at home to the World number one side, Belgium, before a hard-fought goalless draw against The Three Lions in Copenhagen. Those results see them third in the group, a point better off than Iceland, and three behind England, approaching the half-way point.
Christian went off early on during yesterday's defeat to Preston North End and has now been replaced by his midfield partner, Jensen. The 24-year-old is yet to win a senior cap for his nation but does have 31 appearances from Under-18 to Under-21 level, scoring three goals. Mathias was a long-time captain of the Danish Under-21s and was named in the initial 35-man squad for the 2018 World Cup in Russia.
So far this term, Mathias has made five appearances in league and cup for Thomas Frank's Bees. During last month's Carabao Cup against Wycombe Wanderers he set up Ethan Pinnock for the first competitive goal at our new home before suffering an early injury against Birmingham City in our Sky Bet Championship opener. He returned off the bench at Millwall the Saturday before last, then started against Fulham on Thursday and Preston North End yesterday.