PHOENIX -- In order to protect them from the upcoming Rule 5 Draft, the D-backs added four players to their 40-man roster on Wednesday, selecting the contracts of right-handers Riley Smith and Taylor Widener and infielders Wyatt Mathisen and Andy Young.

Widener and Young were the only two players on the D-backs’ Top 30 Prospects list, per MLB Pipeline, who were previously unprotected and Rule 5 eligible. By adding both to the 40-man, Arizona ensured that they will stay in the organization.

The deadline for clubs to add players to 40-man rosters was 6 p.m. MST on Wednesday. The Rule 5 Draft is scheduled for Dec. 12, the final day of the Winter Meetings in San Diego. The D-backs’ 40-man roster now sits at 39 players.

Widener is Arizona’s No. 13 prospect, the highest-ranked unprotected player the D-backs had entering Wednesday. Young is ranked No. 23.

• Tracking the top prospects who earned 40-man spots

This past season, Widener struggled in the hitter-friendly Pacific Coast League, going 6-7 with an 8.10 ERA in 23 starts for Triple-A Reno. But the 25-year-old right-hander had success at every level prior to that, posting a 3.39 ERA in 27 starts for Class A Advanced Tampa in 2017 and a 2.75 ERA in 26 games (25 starts) for Double-A Jackson in ’18, his first season in the D-backs’ organization.

Arizona acquired Widener from the Yankees in a three-team trade that also brought outfielder Steven Souza Jr. to the D-backs from the Rays on Feb. 20, 2018.

Young, 25, was also acquired in a trade, as he came to the D-backs in the deal that sent first baseman Paul Goldschmidt to the Cardinals on Dec. 5, 2018. In his first season in the organization, Young hit .271/.368/.535 with 29 home runs and 81 RBIs in 133 games between Double-A and Triple-A. In 68 games with Reno, Young batted .280/.373/.611 with 21 homers and 53 RBIs in his first career stint at the Triple-A level.

Smith, 24, went 6-6 with a 4.43 ERA in 25 starts between Jackson and Reno this past season. He had a 2.27 ERA in 13 Double-A starts and a 6.89 ERA in the PCL. The right-hander was selected by the D-backs in the 24th round of the 2016 Draft.

Mathisen, 25, was signed to a Minor League deal with a Spring Training invite last offseason. In his first year in the D-backs’ organization, he hit .283/.403/.601 with 23 homers and 64 RBIs in 87 games for Triple-A Reno. He was previously with the Pirates, who selected him in the second round of the 2012 Draft.