Pitcher - Nathan Eovaldi
When great defense by pitchers is discussed, the topic usually begins with Greg Maddux, where a yearly ritual was tossing a GG to him. The Red Sox have never had a GG winner in that position, but the required skill set is limited.
Pitchers are supposed to be adept at fielding bunts and making quick decisions about what to do with them. In the concept of today's game, bunting is rarely employed.
Throwing to second base on a pickoff, when fielding a grounder, or after corralling a bunt is essential. We often see an errant throw chased down by one or more outfielders and watch runners gleefully round the bases. There is a reason why, on infield popups, pitchers are shuttled as far away as possible so as not to interfere with the real fielders and keep the ball out of their hands unless they are pitching.
I was impressed with Nathan Eovaldi in Boston, and in his time in The Hub, Eovaldi made just one error. I used the traditional fielding percentage metric of four seasons with a perfect 1.000 for Eovaldi, so keeping the ball quiet was a plus.
Part of defense for pitchers is not allowing a stolen base, which means a runner can take an extra step or two to second since this guy has no throw to first. Eovaldi was skilled at keeping the pilfering below league average, but one statistical quirk exists.
In 2021, "Nasty Nate" had an almost Cy Young Award season and allowed ten steals with no runners caught. That stat keeping runners anchored may be taken with the proverbial grain of salt.
There were others that I remember doing a respectably defensive job on the mound. The athletic Gary Peters could also hit. Pedro Martinez was cat-quick. Bob Stanley was a bulky pitcher (no fat shaming here) and had some skills. On the downside was Dennis Eckersley, whose pitching motion often had him out of position.