DUNEDIN — When Blue Jays prospect Tim Mayza delivered a fastball to Detroit Tigers third baseman Austin Romine on Wednesday, an actual gasp emanated from the crowd of 3,390 at Florida Auto Exchange Stadium.

The pitch was measured at 98 mph. In fact, he hit that number a few times. In his one inning of work in the third, Mayza struck out Romine and right-fielder Steven Moya, both of whom have MLB experience, gave up a single to outfielder Justin Upton and enticed DH Tyler Collins to ground out to third.

The 6-foot-3, 220-pounder has now thrown two innings over two games in Grapefruit League action, striking out four, giving up one walk, two hits and not allowing a run.

Mayza’s stock in the organization has skyrocketed the last couple of years. Jays manager John Gibbons was almost giddy on Thursday when asked about the big left-handed prospect.

“Yeah, you saw him (Wednesday), that was pretty impressive,” Gibbons said. “We always knew he had a good arm, just needs to harness it a little bit, throw more strikes. Everybody thinks he’s got a chance to be really, really good. That appearance (Wednesday), that will get your attention. Every team in baseball is looking for good left-handed relievers. Of course (Brett) Cecil’s gone now, you’re always looking for those guys.”

Mayza’s heat didn’t surprise Gibbons as much as the 25-year-old’s control and slider against the Tigers.

“He can throw up there, but he’s got a breaking ball too,” he added. “I’ll tell you what, if he puts it all together, it’s going to be tough on left-handed hitters. Even right-handed hitters.”

If Mayza’s progression continues, he may be a left-handed option coming out of the bullpen for the Jays this year.

“Right now my fastball is the key,” Mayza, who throws a two- and four-seamer, said. “And that’s kind of been the key to my progression is just fastball command. The slider’s really come along in the past couple of years and that’s been a real good out pitch for me to get guys to swing.”

A native of Pennsburg, Pa., Mayza was drafted by the Jays in the 12th round in 2013 and last season put together a solid season at High-A Dunedin, where he recorded a 1.66 ERA in 48.2 innings while striking out 52 and walking only 15. He struggled a bit at double-A New Hampshire but still posted a respectable 4.11 ERA in 15.1 innings pitched.

It’s his upside — and the fact that he’s a lefty — that has the organization over the moon at his potential.

“He’s throwing hard, but a lot of times guys that throw that hard it takes a while to develop,” Gibbons said. “And really, a lot of those lefties, a lot of times they’re just all arms and legs coming at you. But what he did (Wednesday) was impressive.”

Said Mayza, “The last few years it’s kind of gotten more and more consistent. The more I’m out there the more experience I get, the more confident I am, the more comfortable I am. And the velocity has come along with that. I just want to keep going out there and keep doing what I need to do and control what I need to control and whatever happens, happens.”

Mayza played both varsity baseball and basketball at Upper Perkiomen High School before concentrating exclusively on baseball when he went to Millersville University.

Mayza actually comes from a big hoops background. His dad Jerry played Division III basketball at Allentown College, now DeSales University, while his sister Deanna is guard for the University of Hartford Hawks varsity team.

“I grew up always going to my dad’s basketball (men’s league) games and basketball seemed to be kind of the way to go,” he said, “but when my baseball career started taking off and I was getting college offers in high school, I decided to go that route.”

The Blue Jays are certainly glad he did.

VLAD JR. HIGHLY REGARDED

Highly-regarded Blue Jays prospect Vladimir Guerrero Jr. is getting some major love from the respected baseball statistics and analysis website FanGraphs.

In a recent study by Chris Mitchell, using the KATOH projection system on baseball’s most promising rookie-eligible players, the 17-year-old Guerrero sat No.2 in Mitchell’s top-100 list, a ranking that takes into account players’ performance, age, height and ranking on traditional prospect lists.

Guerrero was also ranked third on a second “stats only” KATOH list. And since that list doesn’t downgrade prospects who lack scouting pedigree, it’s good for identifying statistical standouts who have gone unnoticed.

Last year, the Montreal-born Guerrero hit .271 in 62 games in rookie ball in Bluefield with eight home runs. He is the son of nine-time All-Star and 2004 AL MVP Vladimir.

The Jays signed the young Dominican for US$3.9 million in 2015 when he was ranked No. 4 on MLB.com’s Top 30 International Prospects list. He’ll most likely play at low-A Lansing this season.

“We’re more excited about Vladdy everyday that passes, not just because of our subjective evaluation of his ability, but because of his dedication and true love for the game,” Jays GM Ross Atkins told Postmedia on Thursday.

“His talent and character translated into exceptional performance at the plate, on the bases, and in the field as an extremely young player at a relatively advanced level last year. Likely influenced by that objective performance, public perception seems to be catching up to the way we feel about him, and he deserves all the credit for that recognition.”

sbuffery@postmedia.com