C Willson Contreras
Had Willson Contreras not gone down with a fractured arm, he likely would have been in the running to be on the All-Star roster, perhaps even as the starter. Alas, that is not the case, and his lack of playing time hurt his case. This isn't to say that the catchers ahead of Contreras, his brother, William of the Milwaukee Brewers, and Will Smith of the Los Angeles Dodgers, aren't deserving; rather, this is to demonstrate how good Willson Contreras has been in less time.
Among catchers with at least 180 plate appearances, Willson Contreras ranks third in fWAR with 2.3. He barely edges out Patrick Bailey -- another potential All-Star replacement -- by 0.1 fWAR. Contreras, however, has played in half as many games as his brother, who sits at 2.8 fWAR. Had he been able to play even 70 games this year, and Willson would be looking at a 3-fWAR total halfway through the year.
Contreras's slash line sits at .266/.399/.519, and his .918 OPS is nearly .80 points better than the next-best catcher's OPS, Will Smith (.845). All-Stars are often chosen for their offensive prowess rather than defensive capabilities. Contreras is the best offensive catcher in the National League right now, and he has a strong argument for being the best offensive catcher in baseball right now.
There are only two other catchers who could challenge Willson Contreras as a replacement: Elias Diaz and Patrick Bailey. Neither can tout an offensive profile as potent as Contreras -- .781 OPS and .749 OPS -- and neither has been as productive in limited time as Willson has been. Should Will Smith or William Contreras sit out, departures that aren't likely, Willson Contreras deserves to take their place on the National League roster.