PHILADELPHIA -- J.T. Realmuto said he thinks he can be ready to play by Opening Day.

But if his fractured right thumb needs more time to heal, what do the Phillies do? Andrew Knapp would move into the No. 1 spot. Knapp entered Spring Training as Realmuto’s backup, and slashed .278/.404/.444 with an .849 OPS and 129 OPS+ in 89 plate appearances last season.

• Realmuto breaks thumb, hopeful for opener

“I thought Andrew had an outstanding season last year, and I am very confident in his skills to produce offensively, to handle our staff in a very high rate,” Phillies manager Joe Girardi said Thursday from Clearwater, Fla. “I think we're fortunate to have Andrew as a backup for J.T., because he's really good.”

Knapp’s backup is probably either Rafael Marchan or Jeff Mathis.

Marchan, who turns 22 next week, is considered one of the organization’s top prospects. He made an unexpected jump to the big leagues last season after Realmuto suffered a hip injury in September. Marchan had not played above Class A, but the Phillies needed him after the front office removed Deivy Grullón from the 40-man roster in August.

Marchan is a defensive whiz, which could keep him in the big leagues for a long time. He had not homered in 846 plate appearances in the Minor Leagues, so naturally, he homered in one of nine plate appearances with the Phillies.

Mathis, 37, has played 16 seasons in the big leagues, relying on his defensive prowess along the way. He has a career .553 OPS and a 48 OPS+ in his career. Phillies manager Joe Girardi said the Phils were working on signing Mathis to a Minor League contract with an invite to camp before Realmuto fractured his thumb last week.

“He’s really good at catching and handling a staff,” Girardi said. “He can do a lot of the little things. He was taking BP today and he was bunting and he was doing some hit and runs and I said, ‘You played for Mike Scioscia, I know you can do those things, because I had to defend those things all the time.’

“He’s very good at doing the little things that he has to do to stay in the big leagues. And people love throwing to him, people love when he’s behind the plate, because you felt like everything was taken care of. All you had to do was make pitches.”

Marchan is on the 40-man roster. Mathis is not, which always is a factor when finalizing a 26-man roster.

“Those are decisions that we don't have to make right now, so let's just pray that he heals quickly,” Girardi said. “Sometimes young athletes can heal quickly, so that's what we're praying.”