Dr. Andrews performed preventive surgery back in December on the opposite Achilles from the one injured in 2018. Per Underhill, he will be full-go by training camp.
This sounds like a tendon procedure such as a tendon scrapping procedure, tenotomy, or Tenex procedure. They are performed for symptomatic tendInopathy. They don’t “fix” diseased tendons unfortunately...they just make it less likely that he’ll become symptomatic during the season and possibly can help prevent tearing (though the medical literature is mixed on the treatment as prevention).