The Diamondbacks are on the verge of a deal with free-agent catcher Alex Avila, according to a major league source, a signing that will fill a hole behind the plate created by Chris Iannetta’s departure earlier this offseason. Terms of the deal are not yet known. The agreement is pending Avila undergoing a physical exam. Avila, 31, is coming off a productive 2017 season split between the Detroit Tigers and Chicago Cubs in which he hit a combined .264 with 14 homers and 49 RBIs. His .387 on-base was the second-best in the majors among catchers with at least 300 plate appearances, trailing only the San Francisco Giants’ Buster Posey (.400). He does not rate as highly defensively. According to Baseball Prospectus’ catching statistics, which factor in framing, throwing and blocking, he was the sixth-worst defender in the majors last season.