Bypassed by all 32 teams after being diagnosed with a heart condition in February, Titans defensive tackle DaJohn Harris (left) looked to prove his doubters wrong. Last week, the undrafted free agent earned a spot on the Titans' final roster. (Getty Images)

After moving up draft charts with a stellar performance at the East-West Shrine Game, Tennessee Titans DT DaJohn Harris was left nearly speechless when told he couldn’t participate in the physical portion of workouts at the combine.

When Harris underwent a battery of tests for the Cleveland Browns, a physician discovered a heart condition known as PFO or patent foramen ovale. Although projected to be selected in the middle rounds of April’s NFL Draft, Harris went undrafted. But Harris (6-3, 306) defied the odds again late last week when he arguably became the most surprising inclusion on the Titans’ 53-man roster.

“It was real exciting,” said Harris of making the team. “All I could do was get on my knees and thank God.”

Harris' condition leaves an opening between the left and right chamber of the heart that is present at birth in all humans, according to the Mayo Clinic. For most people, the hole closes by age one or two but remains open for about 25 percent of the population. The clinic states that most people are unaware they even have the condition. Even if detected, PFO usually doesn’t require treatment. When Harris underwent an EKG at USC, the condition went undetected.

The defect was detected in Tedy Bruschi’s heart when the former Patriots linebacker suffered a stroke in February of 2005. After undergoing surgery to repair the defect, Bruschi returned to the field eight months later. Upon his return, Bruschi made two tackles and added five assists in the Patriots' 21-16 win over the Bills. By December, researchers from the Mayo Clinic determined that the condition wasn’t an independent risk factor for a stroke.

Harris didn’t require surgery for PFO, and Harris says the condition hasn’t had any impact on his playing.

Following the combine, Harris visited a cardiologist in Arizona, who determined the hole was natural and normal, according to ESPNLosAngeles. Motivated by the combine experience, Harris impressed teams by running the 40-yard dash in 5.10 seconds at USC’s Pro Day.

“For me, I took it as someone was trying to hold me back,” Harris said. “During my pro day I tried to show that I would never quit.”

Despite the condition, the Titans considered Harris in their meetings before the Draft. Titans coach Mike Munchak indicated that Harris has decent pass rush skills for someone his size.

“We did our homework on him,” Munchak said. “We were talking about it in the pre-draft conversations with our medical team. We felt good about it, so when the draft ended he was one of the guys that we reached out to early. We were thrilled to get him because D-linemen are hard to come by when the draft ends.”

The presence of former Trojans teammate Jurrell Casey on the line made the Titans an intriguing option for Harris when he agreed to terms with the team several days after the Draft. Casey has seen marked improvement in Harris, notably how he flips or rotates his hips to gain leverage when he rushes the passer.

“He’s better at flipping his hips and not disengaging when he’s blocked,” Casey said. “He’s shedding his blockers.”

Titans fill practice squad: The Titans completed their eight-man practice squad with the signings of OG Chris DeGeare, WR Vidal Hazelton and RB Darren Evans.

DeGeare (6-4, 335) started five games for the Vikings in 2010. Hazelton (6-2, 209) entered the league in 2011 and has spent time with the Chargers and Bengals.

Evans, who rushed for 2,119 yards and 22 touchdowns at Virginia Tech, appeared in two games last year with the Colts. The former Hokies back was mentored by Joseph Addai while in Indianapolis.

“He taught me a lot about reading defenses and reading coverages,” Evans said. 

Key veterans return to practice: CBs Ryan Mouton (concussion) and Casey (elbow) missed the preseason finale against the Saints but have returned to practice. They’re expected to play Sunday vs. the Patriots.

Casey suffered his injury in the second quarter of the Titans’ win over the Cardinals on Aug. 23.

“They had a two-minute drill and they did a draw play,” Casey said. “When I went in for the tackle, one of the linemen came in and hit the elbow.”

For more up-to-the-minute news and analysis on the Tennessee Titans, follow Matt Rybaltowski @CBSSportsNFLTEN.