I got this card signed through the mail, probably in 1990. Gregg (not to be confused with this guy) was the 1989 American League Rookie of the Year. He had 27 saves and a 1.69 ERA. He had a few more good years with the O's before leaving via free agency and joining the Braves. He then started having arm problems and bounced around a lot after that. He had one more good year in 1998 with the D-Backs, but was out of baseball after 28 appearences (and a 8.03 ERA) with the Dodgers in 2001.
This is another example of the Baseball Almanac having the same card signed as I do.