2009-10: Hertl skated for the Slavia Prague U18 and U20 teams in the Czech Republic, winning a gold medal with the U18 squad. Hertl was the third-leading scorer for the U20 team as a 17-year-old, scoring 12 goals with 26 assists and 12 penalty minutes. He had 1 goal with 2 penalty minutes in four playoff games. Hertl was dominant at the U18 level – scoring 13 goals with 10 assists in seven regular season games and then adding 5 goals with 6 assists in five playoff contests.
2010-11: Hertl appeared in one game for Slavia Prague in the Czech Extraliga, was was one of four players with 40 or more points on a high scoring Slavia U20 team, and represented the Czech Republic at the 2011 U18 World Junior Championship. Hertl scored 14 goals with 27 assists and had 49 penalty minutes in 33 games for Slavia U20. In four playoff games he scored 4 goals with 2 assists. In six games at the U18 WJC he scored 1 goal and was minus-three with 12 penalty minutes. The Czech Republic finished eighth in the tournament.
2011-12: Hertl was the fourth-leading scorer for Slavia Prague as a rookie in the Czech Extraliga and represented the Czech Republic at the 2012 U20 World Junior Championship. Skating in 38 games, he scored 11 goals with 15 assists and had 22 penalty minutes. After finishing 12th in the 14-team league, Slavia avoided relegation to the first division in the twelve-game playout series. Hertl scored 3 goals with 6 penalty minutes in the post-season. In six games at the WJC, he scored 3 goals with 2 assists and was plus-two. The Czechs finished fifth in the tournament. Hertl was ranked fifth amongst European skaters in Central Scouting's final rankings prior to the 2012 NHL Draft.
Hertl has upside potential to be a centerman who can play in all situations; he can defend, has a long reach, has an ability to strip pucks, can make offensive plays and can play very well in the tight and dirty areas of ice. The talented playmaker can play all of the forward positions and has the physical game to match his offensive skills. The big Czech forward has good quickness and agility when combined with his excellent hockey sense allows him to play at the higher and quicker speed necessary. The first rounder will need very little time to adjust to the North American style of play but must improve his four-step acceleration and stride technique to give him more time and space to use his elite offensive skills at the NHL level.
Hertl could compete for a roster spot at the Sharks’ NHL training camp but San Jose might also try to convince him to play in the CHL or allow him to stay in the Czech league for another year.