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5/18/2013 1:49 P.M. ET

Happ yet to throw off mound due to knee, not head

NEW YORK -- Left-hander J.A. Happ has yet to throw off a mound in Florida because of lingering soreness in his right knee.

Happ is currently working out at the Blue Jays' Minor League complex in Dunedin, but his sprained knee has yet to fully recover from an injury sustained on May 7 in St. Petersburg.

That's when the veteran lefty was struck in the head by a line drive off the bat of Desmond Jennings. The scary incident caused a minor fracture in Happ's skull, but it's the knee that he twisted on his way to the ground that has proven to be the biggest obstacle to overcome.

"His head is feeling fine, his knee is bothering him a little bit," manager John Gibbons said. "When he fell after getting hit he twisted his knee, so that's the big concern right now.

"Somebody's looking at it all the time but no more X-rays. It's just one of those things that's just going to take time. He'll be a while."

Happ's timetable for a return is still somewhat unclear. General manager Alex Anthopoulos was recently quoted as saying he expected Happ to be out anywhere from three to six weeks.

The three weeks would seem highly unlikely as the native of Illinois has yet to throw off a mound, and six weeks would have Happ back in action toward the end of June.

Happ is 2-2 with a 4.91 ERA while striking out 26 in seven starts this season.

JJ to make rehab start at Class A on Monday

NEW YORK -- Right-hander Josh Johnson is scheduled to make his first rehab start for Class A Advanced Dunedin on Monday night.

Johnson has been out of action since April 21 because of soreness in his right triceps muscle. He was originally expected to return during the middle of May, but the discomfort lingered longer than first anticipated.

Toronto's No. 3 starter likely will be out another three weeks as he begins the slow process of building up arm strength and endurance in preparation for a return to the Major Leagues.

"If he comes out of that Monday [start] feeling good, that will be a good sign," manager John Gibbons said. "But I think it will be at least three [rehab starts].

"It's like Spring Training almost all over again. Not quite as bad."

Johnson is expected to pitch approximately three innings in his first start with Dunedin and will then increase his pitch count each time out. With the required four days of rest between outings, it's possible the process won't be completed until the second week of June.

That could also change if there are any setbacks, but as of now the Blue Jays are confident that the inflammation has been eliminated. Johnson would represent a welcome addition to a Toronto starting rotation that is already dealing with an injury to J.A. Happ and the seemingly lost Ricky Romero, who is currently struggling for Triple-A Buffalo.

The 29-year-old Johnson is 0-1 with a 6.86 ERA in four starts for the Blue Jays this season. He has struck out 19 and walked nine in his 19 2/3 innings of work.

Jenkins, Ortiz to start first two games against Rays

NEW YORK -- The Blue Jays have announced their starting pitchers for Monday and Tuesday's games against the Rays.

Right-hander Chad Jenkins will get the call on Monday and will be followed the next day by veteran hurler Ramon Ortiz. The decision previously had been on hold in case Toronto needed to use Jenkins out of the bullpen earlier in the week.

A pair of off-days on Monday and Thursday afforded Toronto the luxury of taking a wait-and-see approach while keeping Mark Buehrle and R.A. Dickey on normal rest. After Buehrle was able to pitch into the seventh inning on Friday night, there was no longer a need to keep Jenkins available out of the 'pen.

"We're good, we're fresh down there," manager John Gibbons said of his bullpen. "[Jenkins] was in case something happened to Buehrle really early or something."

Jenkins made his season debut on May 12 in Boston. He allowed just a pair of runs on seven hits while striking out two. The 25-year-old will still need to have his workload monitored after coming back from a right shoulder injury earlier this season.

Ortiz has been one of the surprise stories in the past couple of weeks after joining Toronto's starting staff. The 39-year-old has allowed just two runs on 10 hits in 12 innings for the Blue Jays after beginning the year with Triple-A Buffalo.

Gregor Chisholm is a reporter for MLB.com. Read his blog, North of the Border, and follow him on Twitter @gregorMLB. This story was not subject to the approval of Major League Baseball or its clubs.