DAVIE, Fla. (AP) — Even when the Miami Dolphins trailed 40-0 in the fourth quarter of a prime-time fiasco, suspended safety T.J. McDonald stuck with his team, watching on TV at home and wishing he could do something to help.

Now he can. McDonald completed his eight-game suspension for violating the league's substance abuse policy, and he's expected to start in his Dolphins debut Monday night at Carolina.

"I can't wait to watch him play," coach Adam Gase said.

Gase believes McDonald provides a significant upgrade for a defense that has backslid of late, allowing 81 points in the past three games. McDonald watched them all from start to finish, even a blowout loss at Baltimore.

"I was glued in, trying to see what things were going wrong," McDonald said Thursday. "I see these guys work every day. You definitely want to see the fruits on Sunday, but when it doesn't happen, I'm not going to turn the game off."

The Dolphins (4-4) signed McDonald as a free agent in March after his suspension had been imposed for his arrest in Los Angeles on suspicion of driving under the influence. He took part in offseason team activities, training camp and preseason games before sitting out the first half of the season.

"We knew what we were getting into with the suspension," Gase said. "We knew it was going to be about this time, and we were just hoping that we were trending upward when this happened, to where we could have that push over the top that could maybe make a difference."

A third-round pick in 2013, McDonald started 53 games in four seasons with the Rams. Now he'll be paired with safety Reshad Jones, who has been the best player in Miami's secondary in recent years.

Both relish contact and are solid in coverage, giving the Dolphins flexibility with their scheme.

"We'll do whatever they ask us to do," McDonald said. "We're both capable of playing deep, playing blitz. It allows us to show different looks. You never know which one is down and which one is back."

The Dolphins have been solid against the run but shakier with their pass coverage. Opponents have a passer rating of 102.6, third-highest in the NFL, and their completion rate of 70 percent is second-highest.

Miami has only three interceptions all season, and the secondary clearly can use reinforcement.

"I definitely want to make my presence felt," McDonald said. "I want to make those pads pop. That's what I'm going to do Monday."

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