"He is [making a good case]," Price said before Friday's game vs. the Cardinals. "That being said, on any good team you have to have the resources to cover the eighth and ninth innings on the days you don't have them -- if it's Jumbo or Chapman.
"Quite often when you've used Chapman, you've probably set up with your eighth-inning guy to get to Chapman, most times. Quite often, we'll be in a situation where both relievers have been taxed and we'll need guys to step in and pitch the eighth and ninth inning."
Price is expecting right-handers like Kevin Gregg, Burke Badenhop and J.J. Hoover or lefties like Tony Cingrani and Manny Parra to also step up and be able to face hitters on both sides of the plate.
"It can't be so easy as matching up the lefty and righty. If we do that all year, we won't have a bullpen by August, I'd imagine," Price said.
So far, Diaz -- who broke out last season as a 30-year-old rookie -- has handled batters of both the lefty and righty variety, and he's not just throwing high 90's mph heat to get outs.
In Thursday's 3-2 Reds win over Pittsburgh, Diaz faced four batters in the eighth, struck out the side and also changed speeds effectively.
For example, the five pitches Diaz threw to Andrew McCutchen for a strikeout was clocked at 85, 87, 98, 89 and 87 mph.
"He had a really good slider," Price said. "I felt like the way you can tell if a slider is a good pitch is by the reaction of the hitter. ... You see McCutchen and some of those guys in there, that were in front of a slider and that comes down to pitch recognition and not being able to identify the pitch until you've made a swing commitment to the ball.
"I was very impressed with the way he threw. He seems to be built for these late-game situations. This year more than last, he'll have some of those opportunities."
Mark Sheldon is a reporter for MLB.com. Read his blog, Mark My Word, and follow him on Twitter @m_sheldon. This story was not subject to the approval of Major League Baseball or its clubs.