Manager Bud Black said Oberg had a procedure to dissolve the clot at a hospital on Saturday and remained there overnight. The Rockies put Oberg on the 10-day injured list Sunday.
Black said the 28-year-old Oberg started feeling heaviness in his arm on Saturday and alerted the training staff. They sent him to the hospital for an examination and the clot was discovered.
Oberg (6-1) replaced struggling Wade Davis as the team closer two weeks ago and picked up his sixth save in Friday night's win over Miami
Oberg has previously dealt with an axillary artery thrombosis, more commonly known as blood clots. In 2016, he had two surgeries to remove them from his right arm and shoulder. He was prescribed blood-thinning medication and missed the last six weeks of the season.
The Rockies recalled righty DJ Johnson from Triple-A Albuquerque.