Josh Johnson finally felt that he was taking a step forward after a miserable season with the Blue Jays.

A little catch before Tuesday's game was all it took to wipe away his optimism.

Toronto placed the starting pitcher on the 15-day disabled list with right forearm tightness one day before Johnson had been scheduled to face the Boston Red Sox.

The 29-year-old right-hander called the latest twist in his first season with the Blue Jays a huge disappointment, especially after his last start showed promise of a turnaround.

"I finally felt comfortable on the mound. I felt good. I felt like I was getting on top of the baseball and doing what I needed to do to get outs," said Johnson. "Now I'm not able to go out there on the mound. It's frustrating."

Johnson had felt soreness after his start in Seattle last week, but said the arm felt great a few days later and gave him no reason to worry.

The outing against the Mariners, five hits and no runs allowed through five innings gave Johnson (2-8, 6.20 earned-run average) reason to think he was progressing near the end of a lousy season.

The Blue Jays opted to give Johnson extra rest Monday when his start was skipped in favour of J.A. Happ, who was placed on the bereavement list after the game. Johnson's outing was delayed once more by the callup of Todd Redmond from triple-A Buffalo.

But he felt tightness while playing catch prior to Tuesday's game, Johnson described it as a "little grab" in his forearm, and that was all the team needed to hear to place him on the DL.

"Before last start it was the best I felt in three years," said Johnson. "I felt great, everything, shoulder, elbow, everything felt right where it needed to be. I don't know what happened but in my last start I was a little sore and tight. I came in the third day, after the day off, I just felt great that day."

The Blue Jays called up right-hander Thad Weber from Buffalo to fill Johnson's roster spot. General manager Alex Anthopoulos said either Weber or Esmil Rogers could replace Johnson for Wednesday's game against the Red Sox.