Mebane had spent time during the season away from the team tending to Makenna, who was born premature in November with trisomy 13, a chromosomal condition associated with severe intellectual disability and physical abnormalities.
Mebane missed four games during the regular season following the birth of his daughter and was away from the team last week as well. The 33-year-old veteran returned to the Chargers' facility on Wednesday.
"She passed away Jan. 3," Mebane told reporters, per the Chargers' website. "She wasn't getting better so we had to make a decision. She kept having bleeds from the stomach, and then when they tried to feed her, it wasn't good for her liver."
"We're doing pretty good," the defensive tackle said of how his family is handling Makenna's passing. "Just trying to take one day at a time. Still thankful [for having her in our life]. Thank God every day. Still pray. We're just taking it just one day at a time."
After missing last week's Wild Card win to spend time with his family, Mebane told reporters he is expected to play in Sunday's Divisional Round game in New England.
"No matter where I am, I still think about her," he said. "I'm just happy I'm still able to play this game, so [I'm doing] pretty good."