[4] In his second season in the Segunda División B – the only tier in which he competed during his spell in Spain – he scored 16 goals in 37 games, but the side could only rank sixth, thus missing out on the playoffs.

[8] He netted his second against FC Bayern Munich on 25 September in a 2–1 away victory, with a powerful shot into the top corner in what was the Rhineland-Palatinate club's sixth consecutive win of the season, in an eventual run of seven.

[11] On 1 August he signed a contract extension with the club running until June 2015[12][13] and, on 27 October, scored his first hat-trick for the team in a 3–0 home defeat of TSG 1899 Hoffenheim.

[15] On 15 April, Sky Sports published an article on the player where Horst Heldt, general manager of FC Schalke 04, reportedly showed interest in signing him, pending the club's qualification for the UEFA Champions League in order to fund the transfer.

[17] After making his official debut against amateurs FC Nöttingen in the first round of the DFB-Pokal,[18] he played his first league match against Hamburger SV, scoring the hosts' last goal in a 3–3 draw after a shot from Christian Clemens was poorly handled by René Adler.

[24] Szalai was sent off for the first time in his career on 22 November 2014 after committing a foul on Dante in the 90th minute of the league fixture against Bayern Munich at the Allianz Arena,[25] being banned for two matches by the German Football Association.

[26] On 12 December, he replaced Anthony Modeste at the hour-mark of a home game with Eintracht Frankfurt; he scored the 2–2 equaliser three minutes later, and in the 87th he provided an assist with his ankle for Roberto Firmino's winner.

[43][44] After an 8–1 defeat in the Netherlands for the 2014 World Cup qualification campaign, Szalai took part in a press conference where he gave poignant answers about what he thought the reasons behind the long-term underachievement of the national side were.

[47] On 13 November 2013, Attila Pintér, manager of Hungarian League club Győri ETO FC, reacted to Szalai's statements and doubted his honesty.

[50] On 4 September, he posted an announcement on his Facebook profile saying that he did not want to play for his country as long as Pintér was in charge,[51] and thus became the second Hungarian footballer in 20 years to renounce to the national side after Szabolcs Huszti in 2007.

[57] After the victorious qualifying play-off match against Norway, he was recorded on video attending a bar in Budapest where fans were celebrating, and after giving a rousing speech about how they suffered the most during the unsuccessful period of Hungarian football, bought 200 shots of pálinka for the people present;[58] the next day, he jokingly noted in a Facebook comment that he did not remember giving a speech.

[60] He started and scored the opening goal in their first game in the tournament, a 2–0 defeat of Austria in Bordeaux[61] which marked his first after a 40-match dry spell that lasted over a year;[62] shortly before this happened, the Hungarian fans were chanting the name of fellow striker Dániel Böde, demanding a substitution.

[68] His first game was a 1–1 home draw against the Netherlands in the Nations League,[69] with player Zsolt Nagy having previously commented that Szalai's addition could be a motivating factor.