After being sent off the field at last month's minicamp for being overweight, Pierce hired a chef, spoke to the team's nutritionist and ran every day. Currently around 360 pounds, Pierce passed Baltimore's conditioning test and made some plays during his first practice of the year.
"Like I told my teammates, I really apologize for letting them down, and [that] has never been indicative of my character to come in out of shape," Pierce said after practice. "I told them it wouldn't happen again."
Pierce, who is considered one of the top young run-stoppers in the league, didn't attend any offseason practices this spring and looked much heavier than his listed playing weight of 340 pounds when he reported to mandatory minicamp in June. Following the stretching portion of practice, Pierce left the field after speaking with coach John Harbaugh.
"I wasn't diligent in my dieting and wasn't diligent in my conditioning," Pierce said. "I was focusing more on lifting. That was a mistake I learned from. That really, really won't happen again. That's going to be my mission -- to prove to guys that I'm here to work."
While not practicing at minicamp, Pierce worked out twice a day with strength and conditioning coach Steve Saunders. He spoke to the team's director of sports nutrition Sarah Snyder about caloric intake. He hired a chef who put him on a paleo diet.
Perhaps the most impressive part of Pierce's significant weight loss was that he did so even though he took a trip to Italy this summer. Pierce said he would have canceled his overseas vacation if not for the fact that he had paid for it in December.
"I traveled with the scale. That was the thing," Pierce said. "I ate a lot of seafood."
Pierce, 26, ranked as the fifth-best interior defensive lineman by Pro Football Focus last season. He received a second-round tender this offseason and will earn $3.095 million.
He signed as an undrafted rookie out of Samford in 2016, and his weight had previously never been a major issue. This is an important year for Pierce, who can become an unrestricted free agent after the season.
Harbaugh was impressed by Pierce's progress.
"He's maintained his muscle mass and lost the bad weight, the fat weight," Harbaugh said. "He still has a ways to go, but he passed the conditioning test. I think that's quite an accomplishment, especially for a big man like that. I'm impressed with what he's done and very confident he'll get the job done."
The Ravens' conditioning test is considered one of the toughest in the NFL. Players must run a total of 900 yards, and it's broken into six timed intervals.
"Was I worried? No. I know he is a professional," Pro Bowl defensive tackle Brandon Williams said. "Sometimes it gets away from you. It's happened to me before also. I'm not going to fault him for that. If he had come in and not looked as good as he does now and didn't pass his conditioning testing, then there would have been a problem."
The Ravens believe they will be able to welcome back another integral player in the near future.
Wide receiver Marquise Brown began training camp on the non-football injury list as he continues to recover from January foot surgery. But he passed his conditioning test and will be on the field when he is cleared by the team's medical staff.
"That's in the doctors' hands right now in terms of the healing process," Harbaugh said. "No setbacks. He's on schedule. I think they want to make sure this cut and that cut doesn't feel pain. They're probably erring on the side of caution to some degree. I don't want to put a time frame on it because it's never in the coach's hands. I'm hopeful, and I'm really expecting him back here pretty soon."