"We have 25 people, but it's not the official 25 yet," manager Brad Ausmus said. "Anything can happen in 48 hours."
Hardy made a very good case to give the Tigers a third lefty reliever alongside Phil Coke and Ian Krol, taking the momentum he built from last summer's stretch run at Triple-A Toledo. He threw nine scoreless innings to start out camp before giving up four unearned runs March 18 against the Jays and three earned runs March 20 against the Nationals.
"Blaine was a guy who kind of worked his way into the discussion as being one of the possible left-handers," Ausmus said.
The 27-year-old went from a non-roster invitee to one of the final cuts of camp. Asked if the news was tough to take, Hardy smiled.
"It's not that tough, considering I came to Spring Training without having much of a chance," Hardy said. "I came to Spring Training really not expecting to make the team. That's what happened. The best part was that I actually got to show them how I pitch, and they're able to have that in their back of their heads when they're going down the Triple-A roster looking for someone to call up.
"The opportunity was there and I was able to seize it."
Hardy is expected to open the season with the Mud Hens, working out of the bullpen. He had been a starter down the stretch in Toledo last year.
Marinez, signed over the winter as a Minor League free agent, gave up 10 runs (seven earned) on nine hits over 6 1/3 innings this spring. He walked seven and struck out six. He had a rough opening outing, allowing six runs in two-thirds of an inning on Feb. 28. The right-hander then followed that with a great middle run before struggling near the end, walking five batters over his final three outings to lead to four runs.
"He actually has a good arm," Ausmus said. "He throws hard and has the potential to have a wipeout slider. I just think it's more about commanding the ball in the strike zone, getting ahead of hitters."
Jason Beck is a reporter for MLB.com. Read Beck's Blog and follow him on Twitter @beckjason. This story was not subject to the approval of Major League Baseball or its clubs.