La Máquina has all the tools to be a roaringly entertaining comedy thriller. It unites Gael García Bernal and Diego Luna, so effective together in Y Tu Mama Tambien and a handful of other movies, for the first time on the small screen, as an ageing boxing champion and his beloved but deeply dodgy manager. Few duos are better at playing best pals competing to see who is the more lovable screw-up.

Episode one is indeed a riot, dominated by Luna as Andy, a showboating pillock who bluffs through every moment of every day. Clearly addicted to cosmetic surgery – he is described with cruel accuracy as “condom-faced” – and happy to sport a cravat with wet-look hair, his default term of endearment for anyone he speaks to is “asshole” and his motivation is always to earn bigger bucks. At home, however, he is burdened with a wife who is desperate for a child Andy can’t provide and a mother whose close relationship with her son really is much too close. “Only two men have known how to touch me: you and your father,” she says as he dutifully gives her a foot massage.

Andy is a juicy creation, played by Luna with a comic relish not quite matched by Garcia Bernal as the sporting “machine” of the title. Esteban “La Máquina” Osuna, as he describes himself, is a legendary welterweight now rapidly declining. We don’t see the bout he is about to compete in when we first meet him, against a younger, faster challenger: instead we smash-cut from the hoopla of his grand arena entrance to him lolling in a neck brace in the back of an ambulance, asking Andy whether or not he won. Later on, when a doctor asks if Esteban has noticed any cognitive decline, such as seeing or hearing things, Esteban lies and says no. In fact, he has been having strange visions that point to the cracks in his psyche.

Once we learn that Andy is not just a Mexican Del Boy but is properly corrupt and has been fixing Estaban’s bouts for some time, the thriller storyline emerges. Andy has scored Esteban a lucrative tilt at the unified world welterweight title, but a sinister organisation demands that he throw the match. It becomes clear that these mysterious baddies have frightening power when they issue their ultimatum by taking over the lyric prompt in the karaoke bar where Andy and Esteban are celebrating their latest ill-deserved victory, replacing the song words with a message: Esteban loses, or both of you will be killed.

So far so good, but by the second or third episode of six, La Máquina has punched itself out. Eiza González is much too good for the role of Irasema, a tired caricature of the patient ex-wife: her marriage to Esteban– the father of her children – may not have worked out due to his twin obsessions of boxing and partying, not to mention his loyalty to Andy, a man to whom Irasema is forever having to issue world-weary tellings-off; but by heck she still loves Esteban and, handily, she is also an investigative journalist whose late father was looking into boxing corruption before he died.

That’s one of several story strands that gets forgotten about as La Mâquina focuses far too much on Esteban’s mid-life masculinity crisis. The tendency his visions have to form an unsophisticated running commentary on the action worsens as we slide towards the sadly inevitable hallucination/flashback where all his problems are explained via a tableau of him as a young boy. This will match so exactly with what you’ve predicted, you may groan out loud. Meanwhile, the bad guys are conveniently omnipotent but vague with it, allowing La Máquina to add conspiracy-drama overtones to its already chaotic mix. A scene where a potentially important character is introduced, opens their mouth to deliver some earth-shattering revelation, but is then shot in the head by an unseen assassin is a sign of writing that has lost the run of itself and started pushing buttons at random.

Much as Andy and Esteban long for glory days that may never have been all that glorious, La Máquina is never as much fun as that freewheeling opening episode. Even Garcia Bernal and Luna struggle to follow through on what seems like a classic bromance between two old soldiers tending each other’s self-inflicted wounds. They’re surrounded by too many storytelling elements that fail to work for any profundity or chemistry to evolve. La Máquina bursts with energy at the beginning, but in the end it’s just tiring.

• La Máquina is on Disney+ now.