This is not what the Mariners thought they were getting when they acquired Justus Sheffield.

His first season in Seattle’s organization has been nothing short of disastrous. He was pitching so poorly in Triple-A that the Mariners recently demoted the lefty to Double-A. In MLB Pipeline’s latest Top 100 Prospects list released Tuesday, Sheffield fell from No. 43 to 75.

Sheffield highlighted the package the Yankees sent to Seattle in November to acquire James Paxton. They also traded outfielder Dom Thompson-Williams and RHP Erik Swanson in the deal.

In 55 innings with Triple-A Tacoma, Sheffield was 2-6 with a 6.87 ERA and 1.82 WHIP, walking 41 batters. He made one MLB appearance on April 26, giving up two runs in three innings during a relief effort.

The 23-year-old, whom the Yanks acquired at the 2016 trade deadline from Cleveland along with Clint Frazier for Andrew Miller, was expected to make an impact in the Mariners’ rotation later this season, but those plans now are in doubt.

He made his first start for Double-A Arkansas on Tuesday and allowed one run in five innings on four hits and two walks while striking out seven.

Paxton, meanwhile, has a 3.93 ERA in 11 starts with the Yankees. Paxton has dealt with knee inflammation and has had a couple of hiccups, but he allowed two runs in six innings in his last start on Sunday against the White Sox.