Abu Ubaidah ibn al-Jarrah

Born in 583, ʿĀmir ibn ʿAbd Allāh ibn al-Jarrāḥ became a companion of the Prophet and earned the name Abū ʿUbayda. He commanded a large section of the Rashidun Army under Caliph Umar, the second leader after the Prophet's death, and Umar considered him among potential successors to the Caliphate. In 639, the Plague of Amwas killed him — five years before Umar himself died. He never held the top role, but the fact that his name was on the list tells you where he stood.