Rayo came into matchday three of La Liga's fresh campaign with two wins from two following victories against UD Almeria and Granada, but a first-half blitz from Atletico tore them to shreds.
Within just two minutes, the ever-dangerous Antoine Griezmann found the back of the net, caressing a delicate left-footed volley into the far corner despite the best efforts of a diving Stole Dimitrievski.
One goal very quickly became two for the club from the capital, with Memphis Depay the goalscorer on this occasion.
Arriving in the penalty area to poke home Saul Niguez’s pinpoint cross, the Dutchman displayed the sort of finishing prowess that wasn’t always on display last term, his first with Los Colchoneros.
The visitors were now in full flow, and it wasn’t long before they had a third when a lung-busting run from Nahuel Molina ended with the fullback sliding home a stylish right-footed effort to give Simeone’s side an unassailable advantage at the break.
With the outcome effectively decided, the away side could have been forgiven for taking their foot off the gas.
However, midway through the half, they embarked on another goal rush when substitute Alvaro Morata capitalised on a moment of lax defending to finish confidently from inside the 18-yard box.
More unforced errors were to blame for the visitors’ fifth, as goalkeeper Dimitrievski played the ball straight to a wide-open Angel Correa only for the Argentine forward to sumptuously chip the North Macedonia international.
By this point, the floodgates were well and truly back open, and Atletico were in the mood to give their goal difference an early-season boost.
Morata doubled his tally with a left-footed effort from a tight angle inside the area before Marcos Llorente added his name to the scoresheet with a curled strike following a blistering counterattack, which star substitute Morata was once again involved in.
The result sees Atleti move up to second in the table and, while they may already trail their main Madrid rivals by two points, this result will certainly make Carlo Ancelotti’s charges sit up and take notice.
Vallecano boss Francisco, meanwhile, will look to move on from this debacle as soon as possible, and can at least point to his side’s previous victories in his search for positives.
Flashscore Player of the Match: Alvaro Morata (Atletico Madrid)