EUGENE, Ore. — Oregon's quest to replace quarterback Marcus Mariota has already seen its share of drama.

Talented transfer Vernon Adams finally arrived on campus after a cliffhanger finish to his Eastern Washington career, while Mariota's backup, Jeff Lockie, worked hard to differentiate himself from the newcomer.

Coach Mark Helfrich said that ideally he'd like to name a starter in advance of Oregon's opener on Sept. 5 against — interestingly enough — Eastern Washington. But it depends.

"I don't have a crystal ball," Helfrich said. "It has to play itself out. If that's decided in a week, in two months, then it's decided. You can't put a time frame on it."

It will be difficult for either candidate to step out of Mariota's shadow. The Heisman-winning quarterback set a Pac-12 single-season record for total touchdowns with 58, including 42 via pass, 15 on the run and one touchdown catch. He also set the conference mark for career touchdowns with 136.

He declared his eligibility for the NFL draft shortly after the Ducks fell 42-20 to Ohio State in the College Football Playoff championship game and was the No. 2 overall pick by the Tennessee Titans. Under Mariota, the Ducks finished last season 13-2 and ranked No. 2.

Lockie was his backup last season, completing 21 of 27 passes for 207 yards and a touchdown. But the redshirt junior was impressive in this year's spring game, completing all nine of his passes for 223 yards and three touchdowns while leading his team to a 35-29 victory.

"Coach Helfrich wants competition because that will make us all better," Lockie said. "I don't think any of us can argue against that."

Adams' arrival on campus was delayed until he passed a math class he needed to complete his degree at Eastern Washington, where he was a two-time Big Sky Conference offensive player of the year, amassing 10,438 passing yards and 110 touchdowns in his three seasons.

As a first-year player at Oregon, Adams is unavailable to talk to the media before the season opener. And, since practices are closed, there is limited chance to know exactly how the competition with Lockie is going.

Other things to watch at Oregon this season.

NO TYNER: The Ducks will likely be without running back Thomas Tyner for the season after shoulder surgery. Tyner, a record-setting homegrown prep star, appeared in 11 games last season, gaining 573 yards and scoring five touchdowns, primarily serving as backup to breakout freshman Royce Freeman while he struggled with injuries.

"We'd all love to have Thomas out there; he just provides one more weapon in our offense," Lockie said. "But we've missed guys like that before. It's next guy up."

RETURNEES: The Ducks will see the return of two key players: Bralon Addison and Tyler Johnstone, both making a comeback after significant knee injuries.

Addison, who was Oregon's leading receiver in 2013, is back after tearing an ACL in his right knee last spring, while Johnstone, an offensive tackle, tore his last year during fall camp.

Tight end Pharaoh Brown is also hoping to return after a gruesome injury to his right leg last season in the Ducks' victory over Utah.

WHERE WILL NELSON PLAY?: It could go either way for Charles Nelson, a kind-of hybrid receiver turned cornerback turned back to receiver.

Nelson caught 23 passes for 327 yards and five touchdowns as a freshman last season. Oh, and he also rushed 11 times for 101 yards. And he returned 11 punts for 171 yards and two touchdowns.

For the spring practice this year he played at cornerback. For the start of fall camp, he's listed again at receiver.

"He considers himself more of an offensive player, but we talked about how he's too gifted not to be everywhere, obviously including special teams as a return and cover guy," Helfrich said. "The defense is still trying to fight for him."

DEVON ALLEN'S KNEE: Dual-sport start Devon Allen is planning to be back for the Ducks this season — and back with the track team next spring. The speedy receiver tore the ACL in his right knee during the Rose Bowl last season.

He says there's no exact timetable for his return, but he's been easing into it.

Allen won the 110-meter hurdles title at the 2014 NCAA Track and Field Championships as a freshman then won again at the U.S. national championships. He had to skip track this year because of his injury, but hopes to be on track in time to make a bid for the 2016 Rio Olympics.

FAMOUS NAME: Oregon's roster for the fall includes a walk-on with a familiar last name: Matt Mariota. Marcus' younger brother is hoping to forge his own path with the Ducks as an outside linebacker.