Downing probably substituted for someone else at that point in the game?
That was Downing's only ASG appearance.
Downing was still a catcher in 1979, and took over for Darrel Porter, the AL starter. A check of the AL roster for that game shows that Jeff Newman of the A's, the classic at-least-one-from-every-team All-Star, was the third catcher, and being that it was late in the game, the bench was probably thin.
Downing was no speed merchant but that was still an incredible play to get him. The clip shows a quick shot of Downing rounding third before Parker even got the ball, and I'm figure the runner had to have been halfway between third and home when he made the throw, so that was a pretty incredible throw to get him (and Carter did do an excellent job blocking the plate.)
Growing up in SoCal at the time, the Pirates were probably the coolest team in the league, back then with the mix-and-match uniforms, the stovepipe hats, and Sister Sledge blaring during their games, but Parker was a big part of it. He was definitely and "eye-test" guy and consider among the very best players at the time. A couple things I still remember: When he got hit in the face by a pitch, he came back wearing that modified helmet with the half-football facemask for a while. And then there was this game against the Dodgers in, I think, 1977, when catcher Steve Yeager took a throw from the outfield and Parker went full-force into him trying to score. I swear Yeager went heels-over-head and back on his rear end and somehow held on to the ball. Both he and Parker were shaken up actually, but I was surprised Yeager even survived.
RIP, and I hope the boys are boppin' up there.