Alex Avila has spent the last two seasons as the backup catcher for the Arizona Diamondbacks and he has also spent time as a backup for the Tigers, White Sox, and Cubs in the past few seasons after he was the starting catcher for the Tigers for a number of years.
Last season, he played in 63 games and only hit for a .207 average but due to having more walks than hits, his on-base percentage was above average at .353. That actually got his OPS+ up to league average (100).
Defensively, he was 6th in the National League in Defensive Runs Saved with 7 (minimum of 400 innings behind the plate) and he was right behind Wolters in that category (and Wolters caught more than double the innings of Avila). Additionally, according to Fangraphs, in pitch framing, Avila was 11th among 25 NL catchers with at least 400 innings caught with a 2.8 FRM. Wolters, in comparison, was third to last in the National League with a -8.2 FRM.
Avila’s most recent contract was a 2-year deal worth $8.25 million so if the Rockies signed him for a one year deal, $4 million should be in the ballpark to get a contract done.