Johnson made just four starts for the San Diego Padres in 2016, going 0-4 with a 9.15 ERA. He allowed a Shields-like 20 earned runs on 32 hits -- including nine home runs -- and five walks in 19.2 innings. He didn't pitch a single game after July 1.
According to a report in Thursday's San Diego Union-Tribune, Johnson will miss the entire 2017 season after the elbow surgery.
The Padres can at least say they got some salary relief from the deal. They paid Johnson the league minimum to sit on the DL, which is not ideal, but it's probably preferable to paying Shields $21 million to go 6-19 with a 5.85 ERA.