When Chris is throwing his baseball cards into the shoebox, many of those are from the Topps 1980's and 1990's sets that weren't available until 10-15 years after the setting of the movie takes place.
When Chris returns to the hospital for treatment and visits Tony, Tony is watching a 1990 Texas Rangers game with Nolan Ryan pitching. Ryan didn't join the Rangers until 1989 and the setting of the movies is early 70's as Ryan was still pitching for the California Angels.
White Tony and Chris are fixing the static on the TV, a USFL game comes on. The USFL didn't exist until 1983 more than a decade after this film's setting takes place.
When Tony visits Chris at his house, Chris is organizing his baseball cards from a collectors box of the 1990's model which didn't exists in the 1970's.
Tony and Chris are watching a Phillies-Pirates game where Tug McGraw is pitching to Roberto Clemente. McGraw never faced Clemente as a member of the Phillies as McGraw didn't join the Phillies until 1975 and Clemente had passed away in 1973.