[12] When Spanish football became professional in 1928, Osasuna was placed in the third division, gaining promotion to the Segunda División after the 1931–32 season by winning the playoff against Nacional de Madrid.

The strong support of Navarre for the Nationalist rebels led to Osasuna being offered a place in the 1939–40 La Liga when official competitions resumed, although they had finished last in 1935–36 and should have been relegated;[14] ultimately a play-off was arranged with the other demoted team Atlético Aviación – associated with the Spanish Air Force and thus favoured by the military regime.

In the following rounds, they beat Eibar, Real Unión and Sevilla, until the semi-finals where they were knocked out after losing to Recreativo de Huelva 4–2 on aggregate.

[17][18][19] They had a tough campaign in that season's Copa Del Rey, almost being eliminated in the round of 64 but narrowly beating Segunda División B side Castellón on penalties after a goalless draw.

However, they did not make it to the Champions League group phase, after being eliminated by Hamburger SV in the third qualifying round, leaving the Navarrese to compete in the UEFA Cup for the fifth time.

In the Round of 32, they and were drawn against Bordeaux, progressing 1–0 on aggregate, drawing 0–0 away before winning 1–0 in Pamplona through an extra time winner by Javad Nekounam.

Regarded as severe underdogs, Osasuna not only progressed to the semi-finals but did so in style (a 3–0 away win had virtually sealed the tie, but the Rojillos also won the second leg, 1–0).

In the semi-finals, the club was drawn against holders and fellow Spanish side Sevilla, eventually losing 1–2 on aggregate after a 1–0 home win.

A managerial change resulted in substantial improvement, and Osasuna won the final match of the regular 2015–16 season 0–5 away to Oviedo, finishing sixth in the table and qualifying for promotion playoffs and.

They subsequently won all the playoff games – against Gimnàstic de Tarragona in the semi-final and Girona in the final – to achieve promotion to La Liga once again.

[22] The club celebrated its centenary in October 2020 with a league victory over Athletic Bilbao, albeit the match was played in an empty stadium owing to restrictions caused by the COVID-19 pandemic in Spain.

[23] In May 2021, after decades of silence and alongside other Navarrese institutions, club president Luis Sabalza paid homage for the first time to the members who went through the rearguard Nationalist repression during the Spanish Civil War, on behalf of the board of directors.

[27][28] In recent years however, there have been large periods of time where this rivalry match wasn't played, due to the clubs being in different divisions.

Last updated: June 2018Source: CA Osasuna Note: this list includes players that have appeared in at least 100 league games, have reached international status, or both.