SANTA CLARA, Calif. -- The San Francisco 49ers open 2021 NFL training camp on July 31 at the SAP Training Facility. Here's a closer look at a few storylines:

How soon can rookie Trey Lance be ready to play and push Jimmy Garoppolo for the starting quarterback job?

The Niners have no timeline for Lance to start and there's no need to do it any time soon. Coach Kyle Shanahan said if Lance turns it into a competition with Garoppolo then he's OK letting that play out to a natural conclusion. In other words, San Francisco is prepared to have Garoppolo as the starter and allow Lance time to get settled in before asking too much of him. But there are signs Lance can be ready sooner than expected. Lance had a lot of responsibilities at North Dakota State, which runs a pro-style offense with some concepts similar to what Shanahan does. That should help him adapt. Make no mistake, Shanahan's playbook is a different animal, but Lance has proved a fast learner and capable of making a run at the starting job during training camp even if he ultimately begins the season in a backup capacity.

Will the 49ers' offseason emphasis on durability pay off and allow them to return to contention in 2021?

The Niners' tumble from NFC champions to 6-10 last season was the product of many factors but their onslaught of injuries topped the list. Garoppolo, tight end George Kittle, defensive ends Nick Bosa and Dee Ford, receiver Deebo Samuel, cornerback Richard Sherman and running back Raheem Mostert combined to play in just 37 of a possible 112 games (33%). According to Football Outsiders' adjusted games lost metric (which also factored in players missing games for COVID-19 reasons), the Niners lost 161.6 games to injury, the second-most of any team in the past 20 years. At their end of season news conference, Shanahan and general manager John Lynch acknowledged they would put more emphasis on durability in the offseason. That seemed to be the case as most of their key free-agent signings and draft picks have been relatively healthy during their careers. Despite that, the Niners lost three players -- running back Jeff Wilson Jr., offensive lineman Justin Skule and safety Tarvarius Moore -- to significant injuries during the offseason program. If the 49ers are going to get back in the NFC playoff picture, thing are going to have to take a turn for the better in a hurry.

Can DeMeco Ryans successfully replace Robert Saleh as defensive coordinator?

After four years guiding San Francisco's defense, Saleh departed to become the head coach of the New York Jets during the offseason. Shanahan promoted from within, giving Ryans the opportunity to move up from his role as linebackers coach. Ryans, who was a two-time Pro Bowler at linebacker during his 10-year career, is well-regarded as a rising star in the profession. However, Ryans has never coordinated a defense before and his stepping into some big shoes after Saleh led the Niners to top six finishes in defensive DVOA in each of the past two seasons. Players like and believe in Ryans and he has plenty of talent to deploy but there's likely to be a learning curve that could put a bit more of the onus on the offense to produce, especially early in the season.

Will the potential return of Bosa and Ford allow the 49ers pass rush to rev back up?

In 2019, Bosa and Ford were the Niners' biggest offseason additions. The idea was to supercharge the pass rush and make it the focal point of the defense. It worked. San Francisco tied for fifth in sacks (48) and finished third in sacks per drop back (8%). Those numbers dropped precipitously in 2020 -- the 49ers finished 22nd in sacks (30) 21st in sacks per drop back (5%) -- as Bosa (ACL) and Ford (neck) combined to appear in just three games. Bosa's recovery is on track and he's expected when training camp opens, which is an important development for one of the team's top players. Ford's status is far more uncertain. The Niners have expressed some optimism they will have him in 2021 but when or to what extent remains to be seen. If Ford is unable to contribute, the Niners will need much more from players all over the line, including free-agent addition Samson Ebukam and second-year defensive tackle Javon Kinlaw, if they're going to again lean on the pass rush to lead the way.