SAN FRANCISCO — It’s been a whirlwind week for right-hander José Buttó.Buttó’s velocity was down Wednesday and he told the training staff that he had arm discomfort on the mound, an ominous sign for any pitcher. A day later, the Giants put him on the IL with right arm fatigue, a pretty common issue for pitchers, but on Friday they announced that he has a blood clot in his right arm. Buttó got the diagnosis after a visit with Dr. Jason Lee, a vascular surgeon at Stanford Medical Center. He will undergo a procedure to remove the clot. “Everybody’s concern immediately is going to be with someone’s health,” manager Tony Vitello said. “But he’s a very, very, very well-liked and well-respected guy. So everyone was concerned right away. I think the fact it’s not the worst-case scenario, or it could be worse, is good. Time will tell if it’s a decent layoff or an extended layoff.”Vitello said his understanding was that Buttó has dealt with circulation issues in the past, even going back to his time with the New York Mets. He didn’t want to dive too deep into timelines,...