Calero scored his first senior goal on 31 January 2015, netting the first in a 2–2 away draw against UD Maracena.[2]
Valladolid
On 23 June of the following year he joined Real Valladolid, club he already represented as a youth, being initially assigned to the B-team in Segunda División B.[3] In his only season with the side, he was an undisputed starter, scoring once in 37 appearances.
On 15 November 2017, Calero renewed his contract until 2021.[6] He scored his first professional goal the following 27 May, in a 2–3 away loss against Real Zaragoza,[7] and featured regularly during the campaign as his side achieved promotion to La Liga.
Calero made his debut in the main category of Spanish football on 17 August 2018, starting in a 0–0 away draw against Girona FC.[8]
Espanyol
On 9 August 2019, Calero agreed to a five-year contract with Espanyol for a reported fee of €8 million. His release clause was set at €40 million.[9]