Dak Prescott is entering a contract year, and the Dallas Cowboys are entering a season with plenty of question marks.

Star wideout CeeDee Lamb has been holding out for a new contract, and the Cowboys parted with key contributors like Tyron Smith, Tyler Biadasz, Dorance Armstrong and Tony Pollard this offseason.

Replacing Smith, Dallas’ longtime starting left tackle, could prove to be the most important challenge. He’s been an anchor along Dallas’ line when healthy, and the Cowboys need to protect Prescott while opening holes for what appears to be one of the league’s more underwhelming backfields.

The Cowboys are counting on rookie first-round pick Tyler Guyton to fill Smith’s spot, and there is reason for concern. Though extremely physically talented, Guyton was only a one-year starter at Oklahoma, and he started at right tackle, not left.

If Guyton makes a quick transition to a new position and to the NFL, the Cowboys offense should remain one of the NFL’s better units. If he doesn’t, however, it could create serious issues.

Dallas’ top alternative to starting Guyton as a rookie is probably to move Tyler Smith back to tackle, where he started as a rookie—though that, in turn, would create a void at left guard.

The Cowboys also have a lot riding on rookie center Cooper Beebe, but the success or failure of their offensive line will depend most heavily on Guyton.