Sandro Fabian's $500,000 bonus was the largest the Giants handed out during the 2014-15 international signing period. But now they could lose the 20-year-old outfielder in next month's Rule 5 Draft.

On Tuesday, the Giants made smart decisions on adding pitching prospects Melvin Adon and Logan Webb, along with Sam Coonrod, to their 40-man roster to protect them from the Rule 5 Draft. Fabian was not part of the additions after a highly disappointing 2018 season.

At just 18 years old, Fabian opened eyes by batting .340 with an .886 OPS in the Arizona Rookie League. His promotion to the South Atlantic League exposed his biggest weakness against better pitching, though.

Fabian is ultra-aggressive at the plate, and it's hurt him the last two seasons. While he hit .277 with 11 home runs and 30 doubles for the Augusta GreenJackets in 2017, Fabian had just a .297 on-base percentage and struck out 88 times to 10 walks. This past season, the problem became much worse.

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Last season, Fabian was promoted to Advanced Single-A with the San Jose Giants and struggled mightily. He hit just .200, and his on-base percentage fell to .260 with 107 strikeouts to 26 walks in 112 games played.

Despite the troubling results last season, Fabian still has some of the best upside in the Giants' farm system. In 2018, he hit another 10 home runs, and the now-20-year-old has serious power potential with a plus arm in the outfield.

Leaving Fabian off the 40-man roster was the right decision, as he's nowhere near ready for major leagues. At the same time, the Giants should not give up on him, and he could be a big loss if they lose him.

The Rule 5 Draft takes place at the Winter Meetings in Las Vegas on Dec. 13. Teams can pay $100,000 to select a player in the Major League portion of the draft. If that player doesn't stay on the 25-man roster for the full season, he must be offered back to his former team for $50,000.