- Bats Right, Throws Right
- Height 6' 0", Weight 185 lbs.
He was named the Ontario University Athletics most valuable pitcher for 2008 while playing for the University of Toronto's Varsity Blues team. He pitched particularly well in the OUA playoffs that year, throwing a two hit shutout complete game against the Guelph Gryphons on October 1st. On three days rest, he would throw "eight more remarkable innings, giving up one earned run on two hits to upset the Western Mustangs 3-1, and keep his team in the hunt for the final playoff spot." according to this article in the U of T's newspaper .
After college, Deska signed with the Toronto Maple Leafs of the Intercounty Baseball League and was 1-2 with a 3.12 ERA. In 2007, he signed with the MediaMonks RCH and became the first player with a Polish passport to play in Hoofdklasse. Deska was 3-6 with a save and a 3.70 ERA in the 2007 Hoofdklasse. He fell to 2-8, 4.85 in 2008. In the 2008 European Championship Qualifiers, Deska allowed 2 runs and fanned 12 in 9 innings of work for Poland, leading the Prague qualifiers in K's; Poland failed to advance to the 2010 European Championship with a 2-2 record.
Marek would return to the Intercounty League again in 2010, pitching for the Toronto club. In the 2013 B-Level European Championship, he fanned 11 to beat Switzerland and Lukas Croton. He was third in the event in ERA (1.00, behind Daniel Levine and Petyo Petrov) and strikeouts (behind Greg Hendrix and Evgenii Chernozemsky). During the 2015 B-Level European Championship, he lost to Christian Tomsich and Austria but struck out 13 in a two-hit shutout (0 BB) to beat Eimantas Žičkus and Lithuania. He led the event in ERA (0.71, 1.32 ahead of future big leaguer Dean Kremer), opponent average (.188, .25 behind Kremer) and strikeouts (19, 3 ahead of Kremer) and was 4th in IP (12 2/3, between Kremer and Shlomo Lipetz).
He was 2-0 with a 0.56 ERA and 20 K in 16 IP in the 2016 C-Level European Championship, beating Hungary and then Romania in the finals. He led the event in ERA (.56 ahead of Patrik Nenezic), was 3rd in opponent average (.189), led in innings, led in strikeouts (one ahead of Luka Gakhokidze) and tied Pawel Sztejka for the most wins. He was named the event's MVP.
Deska was again Poland's ace in the 2017 B-Level European Championship. In their opener, he matched Denis Leonov of Russia 1-1 through six but the game was cut short by rain; when it resumed the next day, Artur Strzalka took over. Against Lithuania, he allowed two hits and no runs or walks in six, fanning eight. He was second in the tourney in ERA (behind former Twins farmhand Andrei Lobanov), 4th in opponent average (.190, between Heorhii Hvrytishvili and Denis Leonov), 5th in IP and 3rd in K (15, 2 behind Yauheni Kurhun and Serhii Shtapura).