Louis Riddick and Ron Jaworski wonder if the Cowboys will now draft a defensive lineman instead of Ezekiel Elliott to make up for the potential loss of DeMarcus Lawrence. (1:37)

IRVING, Texas -- Dallas Cowboys defensive end DeMarcus Lawrence, who led the team with eight sacks last season, is facing a four-game suspension to start the 2016 NFL season for violating the league's substance abuse policy, according to a source.

The Dallas Morning News first reported the pending suspension.

The NFL has not announced the suspension, an indication the appeal process has not yet been completed. Lawrence is facing the discipline for using amphetamines, the source said. In February, Lawrence received notice of a four-game fine for violating the substance abuse policy, according to sources.

The Cowboys declined to comment.

If Lawrence's suspension is made official, this would mark the second consecutive year the Cowboys would start the season without two key defensive players. Second-year defensive end Randy Gregory will miss the first four games of the season for violating the league's substance abuse policy.

Last year, the Cowboys didn't have middle linebacker Rolando McClain (substance abuse policy) or defensive end Greg Hardy (personal conduct policy) because each was suspended for the first four games of the 2015 season.

Cowboys defensive end DeMarcus Lawrence, who led the team with eight sacks last season, is facing a four-game suspension for using amphetamines, a source told ESPN. Jeff Hanisch/USA TODAY Sports

Lawrence, who had offseason back surgery, played the best football of his career in the second half of last season. The coaches credited him with 56 tackles, 31 quarterback pressures and 10 tackles for loss as he became a disruptive force.

In 2014, the Cowboys moved up to the 34th overall pick in a trade with the Washington Redskins to take Lawrence. He did not have a sack as a rookie in the regular season, missing the first eight games of the season with a broken foot.

Lawrence spent the early part of this offseason taking classes at Boise State.

Executive vice president Stephen Jones, speaking on 105.3 The Fan on Tuesday, said improving the pass rush remained the Cowboys' biggest need entering the draft.

The Cowboys signed Cedric Thornton, who projects to a defensive tackle spot, and Benson Mayowa, who has two career sacks, in free agency. The Cowboys also visited with free agent Jason Jones.

Ohio State's Joey Bosa, the top-rated defensive end in the draft, has been an option with the fourth overall pick before news of Lawrence's pending suspension. Bosa has visited the club's Valley Ranch training facility, and the Cowboys held a private workout for him in March.