It is not considered serious.
Rosenberg, who could be back in a Grapefruit League game in a couple days, is competing for one of three job openings in the bullpen. He is 0-1 with a 15.00 ERA in two appearances this spring. He has allowed eight hits, six runs (five earned runs) and three walks in three innings. He went 1-2 with a 6.12 ERA in 22 games last season.