[2] Succeeding first-team goalkeepers Alberto and Ludovic Butelle, he was promoted to the senior side during the 2007–08 season, and kept a clean sheet in a 2–0 home win over Villarreal CF on 2 December 2007 which marked his La Liga debut.
[4][5] Asenjo returned to the pitch following his recovery, and ultimately made just short of 50 appearances for the Estadio José Zorrilla-based team before earning a move to Atlético Madrid.
[7][5] Upon his return, he found his place in the squad uncertain and, in December of that year, he was loaned to Málaga CF until the end of the campaign, with teammate Ignacio Camacho also making the move in a permanent deal.
[11][12] With his game time limited in Madrid, Asenjo agreed to a one-year loan deal with Villarreal in July 2013 with the club retaining a buyout option at the end of the season.
[14] Asenjo retained his starting spot throughout the 2014–15 campaign but, on 29 April 2015, in the dying minutes of a 1–0 loss to former side Atlético, he tore his ACL for a third time while attempting to make a save.
[15][16][2] After an excruciating rehabilitation process, he made his return to the squad on 23 February 2016 when he was named on the bench by Marcelino García Toral for the Europa League fixture against Italy's S.S.C.
[28] Asenjo was again called up for the 2007 Under-19 European Championship: in the qualification rounds his role in the team was quite insignificant, but his status changed in the semi-final against France, replacing the injured starter and saving two penalties in the shootout as the country progressed to the final,[29] where he appeared against Greece with another excellent display for a 1–0 win.
[35] In March 2015, Asenjo received his first ever callup to the senior national team, being named in Vicente del Bosque's squad for a UEFA Euro 2016 qualifier against Ukraine and a friendly with the Netherlands.