He is the third member of his immediate family to play cricket for the province. And before the Ford Trophy match was abandoned due to poor weather, the North East Valley right-arm seamer picked up two wickets.
His father, Geoff Blakely, was watching from the sidelines at the University Oval. Thirty-three years earlier, Geoff made his first-class debut for Otago, and Sam's sister, 17-year-old Caitlin, made her debut for the Otago Sparks this summer.
Otago cricket historian Dave Richmond was uncertain whether it was the first time a father-son-daughter combination had represented the province but thought it was ''possibly unique''.
A couple of seasons ago, all three Blakelys played in a club game for Gimmerburn - surely that is a first. Either way, it is a mighty feat.
''My parents said they would not miss my debut,'' Sam said.
''They were pretty proud. They have put a lot of time into me and been there through everything, really.''
With Geoff being an opening batsman, it seemed plausible Sam developed as a bowler heaving down deliveries to his father in the back yard. But he actually started out as a batsman.
''It wasn't until I got a bit taller at about 12 or 13 that I started bowling a bit more. I slowly got chucked down the batting order and up the bowling order.''
The strapping 19-year-old is also a handy rugby player. A No8, he played ''a couple'' of senior club games for Kaikorai and is not planning on giving the winter code away yet. Cricket is his first love and his ''best-case scenario'' is to pick up an Otago cricket contract next summer.
''Eventually the choice is made for you because the seasons overlap so much that you can't juggle two at once. You have to go one way or the other.''
Blakely has been part of the wider training group this season and when he got the news he would make his debut, he got very excited.
''I couldn't wait. It is a dream come true. I spent most of my childhood watching half these boys like Redders [Aaron Redmond] and Nath [Nathan McCullum] play.''
His first over did not go exactly to plan. Fringe Black Cap Rob Nicol gave the youngster a brutal welcome, smashing one of the biggest sixes struck at the venue. The ball came to a rest on the 22m of the rugby field behind the media centre.
''You try not to worry but it is always pretty disheartening to watch the ball sail back over your head and the media box for six. You just try and clear your head and get back to your mark and try and get him out with the next ball.''
The bowler had his revenge, though. Nicol hit a drive, only for Michael Bracewell to pluck the ball out of the air at a short cover position. More good news awaited Blakely when Tom Latham got a nick and the keeper took a nice tumbling catch.
When the players were forced from the field, Blakely had two for 57 from 9.5 overs.
Ian Butler got the initial breakthrough when he trapped Brad Cachopa for two. Having slumped to 35 for three, and then 84 for four, the visitors rallied through George Worker (73 not out) and Shanan Stewart (38 not out) to be 159 for four after 39.5 overs.
Both sides pick up two points, but Otago needed the four points for the win to keep its slim playoff prospects alive. Its final one-dayer is against Auckland at the University Oval on Wednesday.