I realize the OP stated the criterion that the player had to have played on the team in 2020. But it saddens me not to see Trey Mancini listed. Hopefully next year he’ll be back near the top on the hit tool/power tool lists.
I think we need to define what we mean by best hit tool. Iglesias makes contact more than any other hitter on the team. His 2020 K rate was 11.3% and his career rate is 12.1%. Nobody else only the team was below 13%. So if hit tool means making contact with the ball, you could argue Iglesias is no. 1.
Iglesias also has a career BA of .278. Only Mountcastle has a higher career BA than that, and that’s in a very limited sample. Alberto is also at .278, while Hays is at .272.
So, if you are treating power as a separate tool, there’s a real good case to be made for Iglesias’ hit tool, without having to rely on his 2020 outlier performance.
I think fans will be in for a rude awakening if they put 2020 expectations on 2021 Jose Iglesias. Still a decent player by all means but we have pretty overwhelming evidence that he is a below average hitter in the league and just a 39 game sample size of a transformed line drive machine. BABIP was an .407. Career .308. His line drive % was 40% while the leader in LD% in 2019 was 28.5%.