CHICAGO -- Shawn Estes had nothing left to prove. The veteran lefty had 99 wins over a solid 11-year career before an elbow injury sidelined him after one start in 2006.

No one would've blamed a then 33-year-old Estes if he would've opted for retirement rather than endure the long, grueling rehab process that accompanies Tommy John elbow reconstruction surgery.

But after all the hard work and determination, Estes is back on the mound and made his first Major League start since April 5, 2006, on Tuesday night against the Cubs at Wrigley Field.

"It's a tribute to him -- the perseverance and hard work that he put in over the last couple years to regain Major League form," Padres manager Bud Black said.

Estes pitched in the Minors briefly last season, going 0-2 with a 4.45 ERA in 11 appearances overall, but he understandably struggled in Triple-A in four outings, posting a 9.82 ERA.

This season in Portland, Estes looked much stronger and was 4-2 with a 3.67 ERA in six starts before the promotion.

"I didn't see him in the games at Lake Elsinore or Portland [last season]," Black said. "I saw the game reports. I heard the scouting reports. You can just tell from those that he wasn't even close to return to the Major Leagues.

"It takes time when you have an injury of that magnitude, especially at this point of his career. It's not an easy thing to come back from. Along the way, there are ups and downs and frustrations, but he persevered. It really looks as though he's regained his stuff, his velocity, the action on his pitches."