its not about him taking playing time from some shitty player its about his development as a player.

If they fuck his career by calling him up too soon then that could seriously harm the team's ability to win baseball games when they're actually trying to contend.

Now, a contender is different. The A's are arguably rushing top prospect Jesus Luzardo up, but they won 97 games last year. The cost benefit analysis is different. The possible benefits in 2019 to Luzardo being up opening day for the A's is far greater than the possible 2019 benefits of Eloy making the opening day white sox roster because those extra couple months of Luzardo vs. someone else could actually be the difference between playoffs and no playoffs.

2-3 months of Eloy on the 2019 sox is probably the difference between 90 losses and 92 losses. The development risk (note that I said development risk, not service time) is less palatable because the upside in 2019 is limited.