The 49ers’ pre-draft roster has taken shape, and most of the team’s starting jobs appear obvious at this stage.

Things will come into sharper focus at wide receiver with the 49ers’ actions in the first round of the 2020 NFL Draft. The 49ers have selected a wide receiver in 17 consecutive drafts, and San Francisco will undoubtedly extend that streak with one of their top two selections -- Nos. 13 and 31 overall -- or with a trade-back option.

The 49ers have to replace wide receiver Emmanuel Sanders and defensive tackle DeForest Buckner, and they will probably use a combination of players to fill those spots.

But here are three positions that shape up to have good head-to-head competitions in training camp:

Dre Greenlaw vs. Kwon Alexander

Dre Greenlaw went from being a part-time player as the strongside linebacker to an every-down player at weakside linebacker when Kwon Alexander sustained a torn pectoral.

When Alexander came back for the postseason, Greenlaw remained in the every-down role. Now, there figures to be competition between Greenlaw and Alexander to determine which player will remain on the field in nickel situations when one linebacker leaves the field.

Greenlaw proved to be a quick study as a rookie. He made the defensive play of the season last season when he saw what was coming and reacted quickly to stop Seattle Seahawks tight end Jacob Hollister just shy of the end zone on a fourth-down play in Week 17 to clinch homefield advantage throughout the playoffs.

Although Alexander was a big-ticket acquisition last year, Greenlaw earned the right to at least compete for the every-down job based on his performance over the second half of the season.

Emmanuel Moseley vs. Ahkello Witherspoon

Ahkello Witherspoon started the season strong after a disappointing second season. When he missed several games due to a foot injury, Emmanuel Moseley stepped in and held his own.

Then, Witherspoon struggled after returning to the lineup, and Moseley generally played well in the postseason after taking over.

The 49ers could use a pick on a cornerback during the first day or two of the draft. But, as of now, it appears to be Moseley vs. Witherspoon. There is added motivation for Witherspoon, who is entering the final year of his contract before hitting unrestricted free agency.

Moseley would enter camp as the clear favorite, but Witherspoon will have the opportunity to make some noise with a strong training camp.

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Tom Compton vs. Daniel Brunskill

The 49ers released starting right guard Mike Person after agreeing to terms with Tom Compton, who joins his sixth NFL team of the past six seasons. Compton has been a backup throughout his career, but coach Kyle Shanahan obviously sees something in Compton he likes. He coached him in Washington and Atlanta.

Brunskill served a valuable role for the 49ers last season due to his versatility. He started games at right tackle, left tackle and right guard. Brunskill should benefit from a competition, where he can focus on playing just right guard.

Brunskill showed he can step into the lineup and play at a high level. He is 26, and he should continue to improve for a while -- especially if he’s able to concentrate on just one position.