That includes continuing to hold dialogue with former Pittsburgh Steelers star outside linebacker James Harrison, according to his agent, Bill Parise.
Former Ravens strong safety Dawan Landry is another possible link for the Ravens after being cut by the Jacksonville Jaguars.
Spears is a 2005 Cowboys first-round draft pick who was selected 20th overall out of LSU.
He was cut this year after signing a five-year, $19.2 million contract in 2011.
Spears, 30, has 226 career tackles and 10 sacks with three forced fumbles. Last season, he had 25 tackles and a sack in six starts.
A natural 3-4 defensive end at 6-foot-4, 315 pounds, Spears was released after the Cowboys hired defensive coordinator Monte Kiffin and changed their primary base defense to a 4-3 front.
The move reunites Spears and Canty after both entered the NFL with the Cowboys eight years ago.
Ravens general manager Ozzie Newsome has made strengthening the defensive line a priority and has already signed former New York Giants defensive tackle Chris Canty to a three-year, $8 million contract since the start of free agency.
“The base of a good defense is to be good along the defensive line,” Newsome said in a statement. "We didn’t play to our standards last season, partly because of injury. With the expected better health of players like Haloti Ngata and Pernell McPhee and the additions of Marus Spears and Chris Canty, we have a chance to improve.
"Spears, like Canty, can play multiple positions along the line. He brings a lot of snaps and big game experience to us. We like the way Marcus plays. He will fit in with the Ravens way of playing.”
Meanwhile, tight end Dennis Pitta, who was assigned a second-round tender of $2.023 million, was the subject of two preliminary inquiries from NFL teams, according to sources.
Because Pitta wasn't assigned the first-round tender of $2.879 million, the Ravens are slightly vulnerable should another team submit an offer sheet. They own the right of first refusal to match any offer sheet. If they didn't opt to match, and no one has submitted an offer at this time, they would be compensated with a second-round draft pick.
The restricted free agent market is notoriously dead, but NFL teams do have a high opinion of Pitta.
It's unclear if the interest of teams will translate into any action regarding Pitta, though.
The Miami Dolphins, who had a high grade on Pitta coming out of BYU, filled their tight end spot with former New York Jets starter Dustin Keller on Friday.
The 49ers are another team believed to be interested in addressing the tight end position.
No offer sheet has been submitted for Pitta, though.
Pitta is a young player the Ravens would ideally like to sign to a long-term deal in the future.
Wide receiver Anquan Boldin returned to the United States on Friday following his relief trip to Senegal. The soonest he would take a physical with the 49ers to complete his trade from Baltimore would be Monday.
After Boldin declined a $2 million reduction of his $6 million base salary, the Ravens traded him to the 49ers in exchange for a sixth-round draft pick