The Twins defense looks pretty bad. I started looking through the Steamer predictions for good defenders.
The top free agent defender, by a large margin, is JT Realmuto with a 10.3. He's the #5 ranked defender in the entire set of projections and the #1 catcher. He would make every pitcher on the roster look better.
The next highest free agent defender is also a catcher - Reese McGuire. If the Twins signed McGuire and traded Jeffers to the Phillies it would improve their defense but not much as it hurts their offense.
Alex Bregman is the highest ranked non-catcher with a 1.8 Def ranking. Next on the list is Isaiah Kiner-Falefa with a 1.1 Def rating. Bo Bichette is next with a 1.0 Def, then Jorge Mateo with a 0.7.
Harrison Bader is the top ranked free agent outfielder by DEF with a 0.7 rating. Byron Buxton gets a -1.4 for comparison.
Josh Bell is ranked 4168 out of 4193 when you sort for defense with a -11.3 rating. DEF is a combined positional and defensive ability metric which means time at DH will hurt your rating. Nevertheless, that's terrible.
Trevor Larnach gets a -8.4 rating. Matt Wallner -7.0. Alan Roden -3.6. Kody Clemens -3.5 (good for a 1B), Miguel Andujar -3.8. Eric Wagaman -2.2 (but only 117 PA of projected playing time). Austin Martin -2.8 which is average for a LF.