"Anybody." "Anywhere." I haven't seen Carlos Santana squatting behind the plate, nor Jose Miranda patrolling center field. Buxton and Correa are playing exclusively at the skill positions they are being paid to play. Vazquez started one game as emergency third baseman. Reputed butcher at second base, Edouard Julien, has played all his innings there this year. Larnach, Wallner, and Margot cycle through the two corner OF spots, with occasional cameo CF appearances by the latter. Kepler plays RF and is rumored to have balked at backing up CF.
Willi Castro, mentioned above, is the one true "anywhere" guy, but if I'm being fair he's not really so good defensively such that he would push a legitimate starter out, and is best used when plugged in due to injuries - 20 games played at 5 positions is testament to both versatility and a lack of elite skills.
I get the feeling some particular play yesterday may have triggered your observation. I watched part of the game, but may have missed a botched play by Brooks Lee? I've seen him make some really fine plays so far, but as with any rookie there are going to be growing pains. Can't think of anyone on the roster I'm less worried about in the long run (like, two months from now).
Seems to me what we are seeing is a combination of talent but youthful inexperience (Lee), and some players with definite and uncorrectable defensive limitations (Julien, Martin). Martin's arm is a liability whether he plays at 2B or CF and there's nothing to be done about it except live with it or else discard him, because the bat doesn't play at LF or 1B where his arm might be least harmful; Martin plays "anywhere" because he actually can play (well) "nowhere."
It would help to know who you have in mind.