DETROIT -- Detroit Tigers starter Jordan Zimmermann, who is on the disabled list with a right neck strain, made a significant step toward his return from injury on Tuesday, throwing off a mound for the first time since Aug. 4.

The 30-year-old Zimmermann threw 20 pitches off the mound and was encouraged by how he felt.

"Feeling good. Finally," Zimmermann said prior to Tuesday's game against the Kansas City Royals. "Last time I probably came back a little bit early and pushed myself."

Zimmermann, who spent July on the DL with a right neck strain before coming back earlier this month, said this time around he will take a much more cautious approach to his return.

While the team was away on a seven-game road trip that featured stops in Seattle and Texas, Zimmermann visited Dr. Liz Wheeler of Launch Sport Performance in Rockville, Maryland, a physical therapist he worked with while playing for the Washington Nationals. She helped identify some issues contributing to his lingering neck issue.

"[She] kind of noticed some muscles that weren't really doing a whole lot," Zimmermann said, "So [I] got those fixed, and I've been feeling much better."

Those muscles were contributing to the persistent neck strain that landed him back on the DL following his last start, which was an abbreviated -- and uncharacteristic -- 1 2/3 innings.

"Basically, the neck was tight and all locked up and we were treating the neck and everything, but something else was obviously causing the issue," Zimmermann said. "The body's a big chain, so we just went down the chain and found a couple things that were pretty tight and got those loosened up for a few days, and now it's just doing a few exercises to stay on top of it."

Zimmermann, who got off to a sensational start in Detroit with a dominant April, will throw another bullpen session Thursday and is slated to throw a simulated game Sunday. After that, he will require at least two rehab starts, according to manager Brad Ausmus.

The Tigers are without Zimmermann, the team's No. 2 starter, and Mike Pelfrey, who is on the DL with a back issue. The club is also missing position players Nick Castellanos (hand), Jose Iglesias (hamstring) and Cameron Maybin (thumb), all of whom are on the DL. The Tigers' lone 2016 All-Star, first baseman Miguel Cabrera, will sit out Tuesday's game with a left biceps strain, though the team is not concerned about him missing more than two to three days at the most.