Source: Baltimore Ravens QB Lamar Jackson expected to start Tuesday vs. Dallas Cowboys

OWINGS MILLS, Md. -- Baltimore Ravens quarterback Lamar Jackson is expected to start in Tuesday night's game against the Dallas Cowboys, a source told ESPN's Adam Schefter.

Jackson, who tested positive for the coronavirus on Thanksgiving, completed his 10-day quarantine Saturday and could be activated off the reserve/COVID-19 list Sunday. The reigning NFL MVP was eligible to practice Sunday and can participate in Monday's walk-through before the game against the last-place Cowboys (3-8), which was rescheduled twice because of the Ravens' recent COVID-19 outbreak.

Ravens coach John Harbaugh declined to comment on Jackson's status or whether he participated in Sunday's practice.

"I know there are going to be questions about the guys who are coming off the COVID list and whether they'll play or not," Harbaugh said. "It's a medical decision. It's really premature for me to comment on any of that at this point. I don't know until the medical decisions are made finally. We don't talk about who comes off that list ever until the transactions are official on the NFL wire. That's our policy."

Asked if Jackson had practiced: "I'm not commenting on any of it. I'm not. I'm just going to stick with our policy on that."

On Sunday, the Ravens abruptly announced that practice had been moved indoors just 15 minutes before the scheduled start of practice. This closed practice to the media, which was unable to see whether Jackson or other players were participating. Harbaugh said the change in practice was due to the wind, which, according to weather web sites, reached 13 miles per hour at the facility.

The Ravens don't have to announce that Jackson has been activated yet because there is no NFL transactions wire Sunday. Baltimore can wait until Monday at 4 p.m.

Asked if not commenting was tactical, Harbaugh said, "That's a by-product of the situation. It is what it is."

Harbaugh then addressed "the conspiracy theorists," saying, "I'm thinking there was somebody on the grassy knoll, too."

Harbaugh mentioned players can get activated off the reserve/COVID-19 list and practice, but the medical staff still need to see how those players respond to the physical activity through a series of tests before clearing them.

Over the past few days, Jackson has been "fully engaged" in the virtual meetings and watches film of what the Ravens are doing at practice, offensive coordinator Greg Roman said.

"So, he's really lockstep, each and every step through," Roman said. "The only thing he can't do is, obviously, be here at the facility and actually take part in it. But, mentally, he's right on it."

The return of Jackson is timely because backup Robert Griffin III, who filled in for Jackson in a 19-14 loss in Pittsburgh last week, was placed on injured reserve Friday with a hamstring injury. That left Trace McSorley, a 2019 sixth-round pick who has thrown six career NFL passes, as the only quarterback on Baltimore's active roster. McSorley will now serve as the primary backup to Jackson.

A year after becoming the second unanimous selection for NFL MVP, Jackson has endured a challenging season. Entering Week 13, he ranks 21st in Total QBR (61.8), 26th in completion rate (63.4%) and 24th in passing yards (1,948).

Jackson can play Tuesday after being activated two days before the game because there is no official "ramp-up" period for players coming off the reserve/COVID-19 list, according to NFL rules. It's the decision of the medical staff to clear him.

Baltimore (6-5), which has lost three straight games to fall to third place in the AFC North, is getting Jackson back for a critical season-ending stretch. In order to reach the playoffs for a third straight season, the Ravens likely need to win at least four of their last five games, which includes the Cowboys, at the Cleveland Browns (8-3), home against the Jacksonville Jaguars (1-10) and New York Giants (4-7), and at the Cincinnati Bengals (2-8-1).

Jackson is the latest starter to come back for Baltimore, which went through one of the biggest coronavirus outbreaks in professional sports. Over the previous two days, the Ravens activated seven players off the reserve/COVID-19 list, including defensive end Calais Campbell, running back J.K. Dobbins and outside linebacker Pernell McPhee.

Baltimore will still be without tight end Mark Andrews, outside linebacker Matthew Judon and wide receiver Willie Snead IV for Tuesday's game against Dallas, but all three starters should return for the game against the Browns. On Saturday, Ravens president Dick Cass indicated there were at least four strains of the coronavirus found in the Ravens' facility.