EUGENE — Byron Marshall’s body was at Autzen Stadium on May 3, but his mind was somewhere else.

Oregon’s starting running back played in the spring game with a broken heart after his beloved grandfather, Bobby Sullivan, died in April after suffering a heart attack.

“It crushed me. I played terrible after that, honestly. It was just hard,” Marshall said. “My mind was just kind of all over the place because I wanted to be back at home with my family. But they kind of put off the funeral so I could finish off spring ball.

“I wanted to see him one last time.”

The Pac-12’s most productive returning rusher has not been in the spotlight much through the first two weeks of preseason camp.

Coach Mark Helfrich is asked about Thomas Tyner, the tantalizing sophomore talent, during most of his post-practice sessions with the media.

For two weeks coaches have been crowing about Royce Freeman, a 6-foot, 229-pound bulldozer included by Helfrich on a list of true freshmen on track for playing time.

Meanwhile, Marshall — who emerged as the starter over De’Anthony Thomas and Tyner last season — is stealthily preparing for a more substantial role in 2014.

“You’re right, we haven’t talked a lot about him,” running backs coach Gary Campbell said of Marshall. “He’s our mainstay, he’s our leader out there, the guy who knows everything, the guy that can get it done. I’m pleased with him right now.”

Helfrich is not shy about voicing his opinion that Marshall needs to improve his practice habits to take his game to the next level.

With Thomas leaving for the NFL, the graduation of Josh Huff and Bralon Addison out with a knee injury, the Ducks’ running backs should have an opportunity to catch more passes from quarterback Marcus Mariota this season.

“Byron just needs to get the total picture and become a great practice player,” Helfrich said. “That was the key to a lot of the guys around here, whether it was Kenjon Barner, LaMichael (James), all those guys were great practice players.”

RBs can count on Campbell

Marshall had four carries for five yards in the spring game. Meanwhile, Tyner averaged 5.8 yards on 10 attempts and caught a touchdown pass from Mariota.

“It was real hard,” Marshall said of mourning his grandfather and focusing on football at the same time. “Losing someone that close to you hurts. It still hurts sometimes. You have flashbacks thinking about him and stuff like that. It wasn’t a fun thing to go through.”

Marshall grew up in San Jose, California, but his parents, Greg and Tammie Marshall, frequently drove their three children to Stockton to visit Bobby and Dorothy Sullivan.

Those treasured childhood memories endure, but Marshall had a difficult time dealing with the shock of his grandfather’s sudden passing.

“It kind of came out of nowhere. If I was expecting him to go, it would have at least been more tolerable,” Marshall said. “The fact that it kind of happened out of nowhere just kind of surprised me.”

If anyone knows how to grieve and grind entering a season, it’s Marshall’s position coach.

Friday was the one-year anniversary of the death of Campbell’s son, Bryan, who bravely fought Wednig-Hoffman syndrome and its cruel effects for 29 years.

After a brief hiatus from the 2013 preseason camp, Campbell returned to the sideline for his 31st season at Oregon. The Ducks led the Pac-12 in rushing offense, averaging 273.5 yards per game with 42 touchdowns.

“That’s my role here. When I sit in their living rooms, I assure their parents that’s what I’m here for and they can count on me to do that,” Campbell said of being a father figure for his players while they are at Oregon. “When Byron was going through that, I sat down with him and we talked and I let him know that if there was anything I could do I would certainly be happy to do it.

“I was also willing to let him do whatever he needed to do to take care of that business with his family.”

Playing with a purpose

Marshall, a junior, has some important business to attend to between the lines this fall.

The 5-foot-10, 205-pound speedster has the physical skills and instincts for the game to make a run to the NFL.

“He’s a guy, just because of his natural talent, we see this vision of what he can be and we want it to happen as soon as possible,” Helfrich said.

Marshall rushed for 1,038 yards and 14 touchdowns last season despite playing only nine snaps in the loss at Arizona and missing the Civil War game against Oregon State because of an injury.

“I’m hoping he’s obviously going to get better,” Campbell said. “He’s definitely going to be the leader in that backfield. He’s out there helping guys all the time, coaching them up, encouraging them when things don’t quite go like they think they should. Because he knows about that and he knows how to hang in there.”

Marshall cannot wait to take the field at Autzen Stadium again on Aug. 30 for the opener against South Dakota. When he runs out of the tunnel, his mind will be focused on the game and his grandfather will remain in his heart.

“Like a little kid before Christmas,” Marshall said of not being able to sleep the night before practices began. “I love playing, honestly. As grueling as this camp is and how long we’re here and blah, blah, blah, it’s why I came here is to play.

“Everything is better now a little bit. I’m just going to go out and play for him and make him happy.”