Rondon's contract was selected by the Cardinals on Thursday.
Rondon spent the 2020 campaign at the Cardinals' alternate training site, but he failed to make his major-league debut during the shortened season. He'll now join the 40-man roster to protect him from the Rule 5 draft. The 22-year-old posted a 3.21 ERA and 1.23 WHIP over 115 innings at Double-A Springfield in 2019.