Grandal, who has caught 75 games but most recently has seen time at first base, will mostly catch this winter in the Dominican Republic.
"He's a guy who wants to play; he's motivated to play," said Padres manager Bud Black. "His knee feels good. He'll be the first to tell you his knee wasn't 100 percent in the first half of the year. But he's very confident in the knee."
Grandal, 25, was limited to 88 at-bats last season after missing the first 50 games due to a suspension and then needing surgery in August to repair the anterior cruciate ligament in his right knee following a collision at the plate in a July game in Washington.
"I think with Yazzy, it's just getting at-bats. He missed most of last year with the suspension and the ACL ... so he missed almost a full year of at-bats," Black said. "And this year, he was on a little slower program in Spring Training and early in the year, and now the at-bats are high enough now for him to feel good about where he is physically."
Grandal hit two home runs in Thursday's 9-8 loss to the Giants, including a grand slam. A switch-hitter, he's hit all 15 home runs from the left side and is just now to the point where he's able to turn on a ball from the right side.
Even though he played his 35th game at first base Friday against the Giants, and the team hasn't closed the door on him playing there in the future, it still thinks of him as a catcher.
As for Liriano, 23, he entered Friday hitting .226 in 106 at-bats since being promoted from Triple-A El Paso on Aug. 11. He had struck out 38 times in 117 plate appearances and, according to Black, just needs more seasoning. That could come this winter in the Dominican Republic.
"He needs a lot of at-bats against good pitching," Black said. "... His at-bats can be conducted a little bit better. He's got to be ready for the fastball, be ready in fastball counts.
"There are some technical things in the swing that [hitting coaches Phil Plantier and Alonzo Powell] are working with him on. Here, he's let some good fastballs go without a swing."
Liriano missed all of last season recovering from Tommy John surgery to his left arm. He hit a combined .291 this season in two Minor League stops with 14 home runs and 66 RBIs.