Arenado (trunk) said after Sunday's 5-3 loss to Atlanta that he will undergo an MRI on Monday, Jody Jackson of DBacks.tv reports.
Arenado went 0-for-2 before exiting in the fourth inning with an injury that the Diamondbacks termed as left trunk discomfort. The 35-year-old is concerned that he might be dealing with an injury to an intercostal muscle, but the MRI should provide some clarity on that front. Idlemaro Vargas and Tim Tawa would be the top candidates to fill in at third base if Arenado's injury ends up costing him some time.