Jeff Gardner was a middle infielder for the Mets in 1991, the Padres in 1992 and 1993, and the Astros in 1994. When I asked him about his baseball card experiences, he wrote back:
"I have two cards that are not my picture. One is Chris Donnels and another is Brad Ausmus."
Interesting - neither one is mentioned by Beckett. That means it is time for some detective work.
Gardner was teammates with Ausmus on the 1993 Padres. Here are cards of both of them in Padres uniform.
I think the Ausmus picture is this one, 1994 Score. It looks more like Ausmus, I think. Plus Gardner is a lefty and Ausmus is a righty, and the person in this picture is batting righty. The number on the bat knob is 15, which was actually Kurt Stillwell's number.
Donnels is tougher. He and Gardner were teammates on the Mets in 1991, but also in the Mets minor league system. Assuming he is not referring to an obscure minor league card,my guess is it might be this 1992 Fleer card, already an error because it lists him as a pitcher. You can't see much of the batters face here, making it difficult.
However, Gardner only played one game at Wrigley Field as a Met, September 11, 1991. Donnels was also in that game. Fortunately, there was a picture of Gardner in that game in the next day's New York Times. Gardner in that picture appears to be wearing a batting glove, or at least a wristband, while the player on the card clearly is not wearing batting gloves, though you can't really see his left wrist. Also, Gardner's stirrups are higher in the Times picture than the stirrups of the player on the card. Not definitive evidence, but circumstantial. Unfortunately there wasn't a picture of Donnels also.
For reference, here are pictures of Gardner and Donnels in Mets uniforms.