Heston is not really a prospect. He’s 29 years old and this will be his fourth organization since the end of last year. The good news is that he started 31 games in the big leagues with the Giants in 2015, sporting a 3.95 ERA and threw a no-hitter. The bad news is that AT&T ballpark is pretty forgiving and the Giants didn’t feel compelled to leave room in their rotation for him the following year. He spend 2016 in AAA for the Giants, where he was initially not particularly effective (4.25 ERA) and then succumbed to an oblique injury in July before returning in mid-August.
He started this year in Seattle, was designated for assignment and picked up by the Dodgers and now is with the Twins. He has spent most of the year in AAA, mostly starting, and has a 3.89 ERA and 32 strikeouts in 34.2 IP. I don’t see anything in his minor league game log that suggests he has turned any corner.
He was drafted by the Twins back in 2007, albeit in the 47th round, and didn’t sign, but it is not uncommon that the Twins are a little extra interested in guys they have followed for a long time. There also isn’t anything in Heston’s AAA work this year that suggests he should be promoted to the majors, but with catcher Chris Gimenez already making his fourth appearance on the mound this year, this could be just another attempt to add a live (in the literal, not figurative sense of the word) arm.