Jackson took his 14th loss of the season Wednesday, when he lasted only 2 2-3 innings and allowed seven earned runs. He is 6-14 this season with a 6.09 ERA.
Jackson dealt with a similar injury at the end of the 2013 season.
Castro left the team on Wednesday due to a family emergency and is out indefinitely. Bereavement list rules allow for a minimum stay of three days and a maximum stay of seven days.