"It's been an eye-opening experience, but it's been a nice one," Johnson said after joining the team for Friday's series opener in Colorado.
Johnson made a couple spot starts for the White Sox, going 0-2 with a 6.94 ERA over 11 2/3 innings, but he spent most of the season in Triple-A Charlotte, where he established a 2.94 ERA over eight starts.
"For me, it's been a helping hand," Johnson said to describe his role in the Sox pitching staff. "I've had a couple Septembers and a lot of spot starts. Helping out the rotation when I needed to.
"I've just been waiting for my time, for my card to be pulled. The Padres are giving me a great opportunity to go out and pitch."
As manager Andy Green describes it, the spot in the rotation is Johnson's to lose.
"He's hungry, ready to prove himself," Green said. "He's got an opportunity to compete to be in our rotation. He's going to come out, he's going to pitch. How many opportunities he gets will probably be dictated by how well he performs."
Johnson was optioned to Triple-A El Paso after the trade, but he never joined them, going to Class A Advanced Lake Elsinore for some side work before the anticipated callup to the big leagues.
"I've never played in the Cal League, so it's been another experience for me as well," Johnson said. "It was a good group of guys down there, a good staff. I got my 'pen in, I got my work in, got my workouts in, and I'm ready to go. Just over the past few days I got to meet the staff here. I got to talk to Andy Green and [pitching coach] Darren Balsley. It's been a welcoming experience."
This is Johnson's best shot to stick in the rotation since he started the 2014 season in the White Sox rotation. He made five starts in April, going 1-1 with a 6.46 ERA, but after walking in a run with the bases loaded in the second inning on April 25, he spent the rest of his season in Charlotte. Among those five starts was an Interleague trip to Colorado, where he allowed 4 runs on nine hits in 5 2/3 innings.
"No matter where you are, you go out and pitch, no matter if it's in Triple-A Charlotte, or Chicago, or here in Colorado," Johnson said. "Your job remains the same. You go out there and put some Ws up on the board."