Joey Bart is understandably at the top of most Giants fans' minds on this sort of list. When San Francisco took Bart second overall in the 2018 MLB Draft, he was hailed as the heir apparent to Buster Posey who would catch for the Giants for the foreseeable future.
Unfortunately, that isn't what happened. Bart's bat certainly showed up in the minor leagues, but in almost 500 plate appearances in the big leagues he sports just an 81 wRC+. With Patrick Bailey clearly surpassing him as the catcher of the future, the Giants have to wonder what Bart could have brought back in a trade when he was considered one of the best catching prospects in all of baseball and hadn't gotten exposed in the big leagues yet.
It was only two years ago that Heliot Ramos looked like a fantastic outfield prospect who was easily a top 3 prospect in the Giants' farm system. San Francisco's first round pick from the 2017 draft had a ton of physical tools and elite bat speed that pointed to a future as a power hitting outfielder that could contribute on the field in multiple ways.
Unfortunately, Ramos has never really blossomed as a hitter the way the Giants had hoped. The power has shown up here and there, but the questions surrounding his hit tool have only intensified over the years and his limited stints in the big leagues have not gone well. This story could have a happy ending, though, as Ramos has posted a .935 OPS in Triple-A this year. While the shine may have worn off a bit, he could still be a useful piece after all.
Shifting gears away from the minor leagues, we need to talk about Brandon Crawford. Crawford has been a stalwart performer for the Giants since 2011. While the offense came and went at times, he was as steady a defender at shortstop as they come the entire time. In 1561 games with the Giants from 2011 to 2022, Crawford accumulated 30.8 rWAR. That is big-time production no matter how you look at it.
However, there were signs last season that his decline was coming as he posted just an 87 wRC+ at the plate. It is understandable why the Giants didn't want trade a guy as iconic as Crawford, but it is hard not to wonder what they could have gotten for him this past offseason while teams still remembered his 2021 season. Unfortunately, Crawford has struggled mightily this season, is currently on the injured list with a knee issue, and is set to become a free agent at the end of the year.