JACKSONVILLE – The secondary got a bit thinner Monday.

Will Blackmon, the Jaguars' nickel back for the first eight games of the 2014 regular season, will miss an extended period with a fractured left index finger, the Jaguars announced on Monday.

Blackmon, who sustained the injury in the team's loss to the Miami Dolphins, is not expected to be placed on injured reserve, meaning he could return this season.

Blackmon, an eight-year veteran who joined the team as a free agent during the 2013 preseason, said he sustained the injury on the game's first play, and thought at first he had just sprained it severely. He had the area wrapped and played 40 plays Sunday.

"It's not going to put me out for the year," he said, "but only time will tell."

Blackmon had 25 tackles, a sack and a forced fumble entering Sunday's game. He was credited with three tackles Sunday.

The Jaguars' defense played a fourth consecutive game Sunday in which they allowed fewer than 20 points. After allowing 10 points to Pittsburgh, 16 to Tennessee and six to Cleveland, the defense allowed 13 points to the Dolphins Sunday. Two of the Dolphins' touchdowns came on interception returns.

"It (the injury) is frustrating whether we were (coming together as a defense) or not," Blackmon said. "It's more so because the chemistry is showing up. Everybody's playing together. We're trusting each other. Now that we're getting hot and rolling it's really frustrating."

Blackmon's injury came as the Jaguars dealt with another injury in the secondary, with cornerback Alan Ball missing Sunday's game and his status remaining uncertain for the remainder of the season.

Ball, a starter at cornerback in the first seven games of the season, missed the loss to Miami with a biceps injury. He sought a second opinion on the area last Wednesday, and the situation is expected to be updated later in the week. Ball said late last week he didn't think the injury was season-ending.

Ball's status is being evaluated and is expected to be updated later in the week.

Also around the Jaguars Monday, tight end Marcedes Lewis has been cleared to practice beginning Wednesday. He is currently on the NFL's injured reserve-designated to return list with a high ankle sprain and can begin playing November 23 against the Indianapolis Colts.