Buck Allen's celebration with his little brother on Saturday went beyond getting drafted by the Baltimore Ravens in the fourth round. It was a moment for the USC running back to reflect on a journey filled with challenges, tragedy and heartbreak.

"I know when it all calms down later on, I’m going to sit [by] myself, and I just know I’m going to tear up and cry and think about all the stuff me and my family went through to get to this point," Allen said. "It’s a blessing.”

Buck Allen was the only player in the country to record 13 games of at least 100 yards from scrimmage last season. AP Photo/David J. Phillip

To reach the NFL, Allen had to overcome grueling hardships while growing up. Raised by his grandmother, Allen lost his father figure at the age of 12 when his older brother went to prison on attempted murder charges. When he reached high school, he went to live with Mickey and Alice Cullen, assistants at the local Boys and Girls Club. Alice passed away from breast cancer in 2009.

To honor her, Allen writes "Alice" in black marker on tape over his left wrist. After he scores a touchdown, he kisses his wrist and points to the sky.

"It’s a whole lot of emotions," Allen said. "When I first started out, I never had a celebration at all. But [it is about] pretty much letting it all out, and you have so much built inside."

The Ravens selected Allen with the No. 125 overall pick after he led USC in rushing the past two seasons and finished third on the team in receptions last season. In 2014, he ran for 1,489 yards and 11 touchdowns and caught 41 passes for 458 yards.

Even though Allen isn't expected to make the same immediate impact as running backs Melvin Gordon or Todd Gurley, who were selected in the first round, he has the potential to develop into an every-down back. He was the only player in the country to record 13 games of at least 100 yards from scrimmage.

"He has deceptive speed," director of college scouting Joe Hortiz said. "When you watch him, you don’t realize he’s gaining so much ground because he’s kind of a smooth runner. He’s a guy we really liked as a collective group, and he’s going to come in and battle for reps and some time with the guys that are already here."

Allen envisions himself being a backup "for a while" before taking more of the workload. With his ability to catch the ball, Allen could carve out a niche as a third-down back right away.

Running backs are an important part of new offensive coordinator Marc Trestman's passing attack. In his two seasons with the Bears, running backs caught 190 passes.

"Buck was our top guy coming into [Day 3 of the draft]," Trestman said. "We really like Buck. We like his athleticism. We like his size. He’s very good inside and outside. He can catch the football. He’s a good blocker. We were very excited to have the opportunity to get Buck when we did."

As Allen prepares to take the next step in his career, he hasn't forgotten about his past, which has been defined by his perseverance. In a recent Los Angeles Times feature, Allen said he remains in contact with his grandmother and Mickey Cullen, whom he "loves as a father." He has also written his older brother in prison.

Allen believes everything he has endured has helped him get to this point in his life.

"I had to fight to get what I want. Stuff was never handed to me," Allen said. "Even growing up as a kid -- even living with my grandmother -- it was never handed to me as a kid. You always had to fight. You always had to figure out a way. Never give up on yourself. Believe in yourself."