The 13-time Mexican league champions signed Fidalgo only hours after Colombian winger Andres Ibarguen cleared out a roster spot upon being sold to Santos Laguna on Sunday night -- at the very same time both teams were involved in a league fixture that ended in a 1-1 draw.
Fidalgo, an attacking midfielder with national team experience at the under-16 and under-17 levels, was given his only Real Madrid cameo with Solari at the helm in 2018. In a Copa del Rey fixture against Melilla, Fidalgo logged 12 minutes in a 6-1 victory for Los Merengues.
The bulk of Fidalgo's experience thus far has been with Real Madrid B, where he logged 91 league matches and scored 15 goals between 2016 and 2020. In August of last year, Fidalgo signed a three-year deal with Castellon in the Spanish second division, where he played 22 games, starting 12 times.
Prior to the move being announced, Solari expressed his desire for more signings.
"The transfer window has not closed yet," the Argentine manager said after Sunday's match. "I have a lot of experience in football and [I know] a lot of things can still happen in these final hours."