The Dallas Cowboys have high hopes for the 2015 NFL season, but the year hasn’t exactly gotten off to the start that the team was looking for. Dallas suffered a loss in its first exhibition game, and they are dealing with several injuries ahead of Week 2 of the preseason.

When the Cowboys visit the San Francisco 49ers on Sunday, they could be without a few top players. Cornerback and running back are the two positions that have been hit particularly hard with the injury bug.

Just three days after first-round pick Byron Jones made his NFL debut against the San Diego Chargers, he was involved in a potentially disastrous play in practice. The cornerback was helped off the field after he collided with cornerback Morris Claiborne and stayed down on the ground for several minutes. Jones hurt his left shoulder during the incident, but it doesn’t appear to be anything too serious.

“I have been worried ever since he had that fall, but I’ve gotten some information that basically it’s not as bad as it could have been,” owner Jerry Jones said on Sunday.

Byron Jones will get a second opinion on his left shoulder after an MRI came back negative, looking to make sure he didn’t suffer any serious damage. His regular season debut doesn’t seem to be in jeopardy, but the injury will likely force the 22-year-old to sit against San Francisco.

In addition to Byron Jones’ injury, a few other members of Dallas’ secondary are banged up. Brandon Carr missed the first preseason game following hand surgery, and Orlando Scandrick has been sidelined by a sore knee. Claiborne, who has undergone surgeries on both knees in less than a year, might actually be the only fully fit cornerback, as he took reps with the first team on Monday.

Injuries have prevented Claiborne from playing in the preseason since 2012. He missed Thursday’s game in San Diego, but he claims he hasn’t been this healthy since he played at LSU.

All of Dallas’ top offensive playmakers sat out against the Chargers. Quarterback Tony Romo figures to be on the field against the 49ers, but the team will be without other Pro Bowl players. Wide receiver Dez Bryant isn’t expected to play with a hamstring injury, and a strained right biceps should keep offensive tackle Tyron Smith off the field, as well.

Three running backs are competing for carries in 2015, and none of them saw the field against the Chargers. Lance Dunbar participated in a full practice on Monday for the first time in two weeks. Darren McFadden is healthy enough to practice, and he has returned to the field in pads as the Cowboys try to ensure that he doesn’t reinjure his hamstring.

Joseph Randle has a chance to be Dallas’ top rusher this season, and he is back on the field after suffering an oblique injury. Randle played in all 16 games as DeMarco Murray’s backup last year, averaging 6.7 yards per carry.