The 22-year-old bantamweight was making his debut on the undercard of the Leigh Wood v Michael Conlan bout in front of a large crowd and dropped Nicaraguan Hernandez to the canvas in round four on his way to a 40-34 points win.
Leivars, whose dad Julian is among his coaches and who is managed by MTK Global, produced a confident display that saw him land some dangerous combinations, one of them sending Hernandez to ground in the dying moments of the fight.
And the lifelong Mansfield Town fan, whose dream remains to one day fight at One Call Stadium, was delighted with his victory.
He told iFL TV: “There were a few raised eyebrows when I took this fight for my debut as he [Jose] is a very tricky opponent who makes you look messy and there’s a lot of head clashes and rough stuff inside, and it’s something you probably need to learn over five or ten fights how to deal with.
"I hurt him the second round and it made me a bit too eager but once I’d settled myself and got more composed, I brought him onto me where I could put him down, so I learned a lot more than it just being my debut as I beat a tough opponent put in front of me which I’m happy with.
"He knew how to survive – I’d hurt him with a shot and he’d find a way to glance and parry the next few shots and it was tricky to find a way through, but I’m happy with that because if you just go out and blow the opponent away in the first round I probably wouldn’t have learned a great deal from it.
"There are a few things to learn from but from a debut I couldn’t ask for any more.”
Leivars also hailed the support he received, with over 500 fans from Mansfield travelling to watch.
He said: "When I got out there, the nerves melted away and it was just excitement and I had to stand there for a second and soak it in because the support I’ve had over the last few weeks has been absolutely amazing and I couldn’t thank everyone enough, both from Mansfield and from everyone in Nottingham, who have been brilliant.”