The list of Jewish professional athletes that played in Pittsburgh is pretty small. There's Randy Grossman who played tight end for the Steelers in the 1970s, Josh Miller, the Steelers' punter from 1996-2003, and Pirates pitcher Bob Kipper, who is not Jewish but inspired non-Day of Atonement "Yom Kipper" celebrations after any of his victories. While current Pittsburgh Steelers wide receiver Antonio Brown is also not part of this list, he may have started his own group of professional athletes wearing his own team's yarmulke.
This picture is from Brown's Facebook page with no explanation and appears to have been removed (or I just can't find the picture now). I learned that Pittsburgh's Tree of Life-Or L’Simcha held a Sports Night program featuring Brown about a week ago, so perhaps the synagogue presented the wide receiver with the yarmulke. That's my theory.
h/t The Pittsburgh Post-Gazette's Blog 'n' Gold