OAKLAND, Calif. — Brett Gardner was out of the lineup for a second straight game Wednesday night because of an in-grown toenail on his right big toe.

“Better,’’ Gardner said before the Yankees’ 6-4 loss to the A’s on Wednesday night. “I took a full BP on the field.”

Gardner had the toenail removed after Sunday’s game.

“He was pretty sore [Tuesday]. He should be good to go [Wednesday] today,’’ said Aaron Boone, who started Mike Tauchman for a second straight game.

“I had it in spring training, but we weren’t playing games,’’ Gardner said of the issue.

According to Boone, Dellin Betances’ bullpen session in Tampa was encouraging.

“Everything went well, two innings but up and down, two 16-pitch side sessions,’’ said Boone, who said Betances, who has been on the injured list all season with shoulder and lat injuries, could be throwing another bullpen session as early as Friday.

Luis Severino (shoulder, lat) will face hitters in Tampa on Thursday as his rehab continues. … In other injury news, center fielder Aaron Hicks hasn’t been cleared to throw. Hicks is on the IL with a strained right flexor.

Gary Sanchez’s first-inning homer Tuesday was the 99th of his career. Only five catchers in major league history have hit 100 homers by Sanchez’s age (26 years, 262 days as of Wednesday): Johnny Bench, Yogi Berra, Gary Carter, Brian McCann and Lance Parrish. The first three are Hall of Famers.

The Yankees have more to dislike about the Coliseum than the fact that it is a dump. Since the beginning of the 2013 season, the Yankees were 15-25 against the A’s at the decayed venue going into Wednesday. That is the Yankees’ worst record at any AL club’s ballpark in that time frame. They are 7-19 at the Coliseum since July 19, 2012 with four of the seven wins coming in a four-game sweep in 2016.

The Yankees went into Wednesday three games away from tying the Brewers for second place on the all-time list of consecutive games without being shut out. The Yankees had scored at least one run in 209 straight games. The Brewers did that in 212 games bridging the 1978-79 seasons.

The Yankees touched home plate once a game for an MLB-record 308 games from Aug. 3, 1931 to Aug. 2, 1933.