In seeking a sixth successive finish in Serie A’s UEFA Champions League qualification berths, Inter have long known that games such as these against relegation candidates simply must end in victory.
After making the more purposeful start, they were presented with a golden opportunity to seize the initiative less than 15 minutes into the game, when Mattia Caldara was adjudged to have felled Danilo D'Ambrosio in the area.
The usually reliable Martinez stepped forward from 12 yards, but his effort was impressively beaten away by Bartiomiej Dragowski.
From Martinez’s standpoint, that miss would set the theme for an excruciatingly frustrating first-half, and he spurned an equally glorious chance not long after, when Dragowski again proved he had the measure of the Argentine.
His heroics in the net gave Spezia the platform to search for an opener themselves, and they almost found one against the run of play, when Kevin Agudelo crashed an effort off the woodwork to set Inter’s nerves jangling.
Most Inter fans in attendance had now started to get the sense it wasn’t going to be Martinez’s night, and those assumptions were affirmed inside a minute of the second half, when the diminutive Argentine rose highest to head home Matteo Darmian’s cross, only for the offside flag to deny him a second goal in two games.
Those travelling fans were made to feel a whole lot worse shortly after too, as a swift Spezia break resulted in M'Bala Nzola teeing up Daniel Maldini, the son of former AC Milan great Paolo, to fire Spezia into the lead.
From then on, the game followed a much similar pattern, with wave after wave of Inter attack being rebuffed by a dogged Spezia as the game ticked into the latter stages.
But Spezia proved to be the masters of their own downfall in their quest for an unlikely shutout, when Inter were awarded a second penalty of the evening – one which was this time taken on by Romelu Lukaku, who duly converted to set up a grandstand finish.
The game had yet another twist in store though, when the referee pointed to the spot yet again, this time in Spezia's favour.
At the same end where Martinez missed, Nzola made no such mistake in firing home a famous winning goal to steer Spezia closer to safety, and leave Inter looking anxiously over their shoulder with all their fellow top-four challengers yet to play this weekend.
Flashscore Man of the Match: Daniel Maldini (Spezia)
