A week earlier, Fowler won the silver medal in the senior men's discus at the New Zealand track and field championships in Christchurch.
Pirates took its few chances and won the game.
Alhambra-Union blew its numerous opportunities and lost.
Pirates fullback Kieran Fowler kicked four goals from his six attempts to score 12 of Pirates points at the North Ground.
The Alhambra-Union kickers landed just two goals from five attempts.
Pirates had only two serious chances to score tries and took a vital one in the 34th minute of the second spell to win the game.
The opportunity came because Alhambra-Union had blown yet another of its 10 serious scoring chances inside the Pirates 22.
The ball came loose and it was booted downfield with interest.
Alhambra-Union lost control of the ball inside its own 22 and Pirates pounced.
Centre Marshall Suckling scored the winning try.
Alhambra-Union dominated possession and territory in the first half when it led 5-3.
It did not score more points because of wrong option taking, tentative passing and kicking when the line was in sight.
In the final minutes of the game, Fowler made a tackle on Alhambra-Union halfback Jarid Bradley on the Pirates 22 that stopped an attacking movement in its tracks.
Pirates flanker Garth Swan had an outstanding defensive game and lowered the big men in the Alhambra-Union pack by tackling round the legs.
Suckling spearheaded the backline defence and No 8 Warren Kearney led by example and crashed over the advantage line.
First five-eighth Peter Breen had speed off the mark and always looked dangerous with the ball in hand.
He scored a brilliant solo try after 15 minutes in the second spell to give Alhambra-Union a 15-9 lead.
No 8 Matt Kissick was Alhambra-Union's best line-out jumper and flanker Waharai Waitohi had a busy game.
Pirates 17 (Marshall Suckling try; Kieran Fowler 4 penalty goals), Alhambra-Union 15 (Waharai Waitohi, Peter Breen tries; Jone Paumau conversion, penalty goal).
Halftime: Alhambra-Union 5-3.
Referee: Jeff Grubb.
