Diaz (biceps) played catch Wednesday, Charlie Goldsmith of The Cincinnati Enquirer reports.
Diaz was placed on the 15-day injured list Sunday due to right biceps tendinitis, but it's encouraging to see him throwing off flat ground several days after the transaction. Although biceps tendinitis can sometimes lead to more serious issues, the right-hander has made good progress early in his IL stint and doesn't currently appear to be dealing with a particularly severe injury.