In July 2010, Herrerín decided to leave Athletic in search for "a new life in football", signing a contract with Atlético Madrid and spending two full seasons with the reserves also in the third division.[6]
On 8 January 2011, in a match against neighbouring Getafe CF B, he scored the 3–2 winning goal for the hosts in the 72nd minute.[7]
Return to Athletic
Herrerín returned to Athletic Bilbao in summer 2012, signing a two-year deal and immediately being loaned to CD Numancia in a season-long move.[8] He made his Segunda División debut on 19 August, in a 2–0 home win against Sporting de Gijón.[9]
In July 2013, Herrerín agreed to a new contract with the Lions and was promoted to the main squad.[10] On 23 August he played his first match in La Liga, keeping a clean sheet in the 2–0 victory over CA Osasuna at the Anoeta Stadium.[11] He spent his first year, however, as backup to longtime incumbent Gorka Iraizoz.
Herrerín was first choice in the Copa del Rey in the 2014–15 campaign, helping his team to reach the final of the tournament for the first time in three years.[12][13] On 25 May 2015 he signed a new deal with the club, running until 2017.[14]
In 2015–16, Herrerín played both domestic cup and UEFA Europa League games while appearing twice in the league during Iraizoz' red card suspension.[15][16] On 8 June 2016, he agreed to an extension until 2019.[17]
On 30 November 2016, after being overtaken by Kepa Arrizabalaga, Herrerín was loaned to fellow top-tier side CD Leganés until the end of the season, mainly as a replacement for injured Jon Ander Serantes.[18] On 19 January 2018, already back at Athletic and during a domestic league fixture away to Getafe CF, he conceded two penalties by tripping opposing forwards, saving the second kick in an eventual 2–2 draw.[19] The previous week, he had signed a new contract until 2021.[20]
On 7 January 2019, in a league match away to RC Celta de Vigo, a long kick upfield by Herrerín (now the first-choice goalkeeper following Arrizabalaga's departure to Chelsea) was collected by Iñaki Williams who ran on to score, making the former the first goalkeeper to register an assist in La Liga in the 21st century.[21][22] He barely featured in his final two years, due to the emergence of Unai Simón.[23]
Al Raed
On 30 August 2021, Herrerín joined Saudi Arabian club Al Raed FC.[24] The following 15 June, he was released from his contract by mutual consent.[25]
Herrerín made his debut for the unofficial Basque Country national team in May 2019, in a 0–0 draw away to Panama for which a small, youthful and inexperienced squad was selected.[31][32]
^"Iago Herrerín, cedido al Barakaldo" [Iago Herrerín, loaned to Barakaldo] (in Spanish). Athletic Bilbao. 7 January 2007. Archived from the original on 22 February 2013. Retrieved 8 December 2012.