Mättig, who is trained by Janko Neuber and starts for the WSC Erzgebirge Oberwiesenthal , began his international career in junior races in 2005. On January 13, 2007, he started for the first time in a qualification for the cross-country alpine cup in Cogne . After he missed the qualification as 68th, he started again a day later in the junior race and won it. At the following European Olympic Winter Youth Festival 2007 in Jaca , Spain , Mättig ran over 7.5 km in classic style to 15th place, before finishing seventh over the 10 km distance. In March 2007 he was able to collect Continental Cup points for the first time as 24th at the Alpine Cup in Val Casies. In January 2008 Mättig was among the top 20 of the Alpine Cup for the first time in Sankt Jakob im Rosental . In February he won another junior race in the Bavarian Forest . At the Nordic Junior World Ski Championships 2009 in Praz de Lys Sommand , Mättig ran in 29th place over 10 km. A few weeks later he won another junior race in Schilpario . In January 2011, he ran on the podium for the first time in the 20 km pursuit in the Oberwiesenthal Alpine Cup and came third.
At the German Cross-Country Ski Championships 2011 in Hirschau , Mättig was able to secure a national medal for the first time and won the silver medal behind Andy Kühne over the 10 km individual distance in free style . Three weeks later, he was third again on an Alpine Cup podium in Rogla . As a result, Mättig had to be content with rather mediocre placements. It was not until January 2012 that he was again among the top 10 in Arvieux . In February, he narrowly missed another podium in Campra, finishing fourth. For the 2012/13 season Mättig took part in the DSV qualification races for the A-team in the cross-country skiing World Cup , but had to admit defeat to the traditional athletes. In January 2013 he ran at the U23 World Championships in Liberec over 15 km in 25th place. At the European Police Championships 2013 Mättig won a silver medal.
At the German Cross-Country Ski Championships 2015 in Oberwiesenthal, Mättig won the title in an individual race over 10 km. In the pursuit, he won the bronze medal. In the team sprint, he finished fifth together with Lennart Metz . A little later he finished his most successful 2014/15 Alpine Cup season to date, finishing seventh overall.
In addition to cross-country skiing in winter, Mättig has also started irregularly in roller-skiing competitions in summer since 2009. In August 2010 he won the 92 km marathon on the Fläming Skate.
Germany
