Atletico Madrid put one foot in the quarter-finals of the Copa del Rey thanks to a 4-0 first-leg win at Lleida Esportiu, with Diego Costa scoring as a substitute on his return before giving them an injury scare.
Vitolo and Costa only became eligible to play at the start of January following their moves in July and September respectively due to Atletico's transfer ban, and although the game was already won by the time they both entered the fray from the bench, the former Chelsea star made a lasting impression with the final goal.
It was by no means a vintage Atletico display for much of the first half, as they afforded their modest opposition several chances and looked flat going forward.
But Diego Godin headed them into the lead just after the half-hour mark - arguably against the run of play - and Fernando Torres was also on target four minutes later with an easy finish at the end of a fine passing move.
With Atletico's intensity dropping again after the break, Simeone threw on Costa and Vitolo for their first appearances since their respective moves from Chelsea and Sevilla.
And Costa made an almost instant impact, producing a smart finish - and taking a knock in the process - from close range.
A deflected Antoine Griezmann free-kick in stoppage time added further gloss to the scoreline, Marc Trilles sent off for a second yellow card for conceding the set-piece.
For all the star quality in the Atletico side, they simply could not match Lleida's desire during the early exchanges, with the home side looking much more purposeful in attack.
They crafted two decent chances in the first seven minutes, as Ivan Agudo first shot just wide of the right-hand post after cutting in from the right flank, before Manu Molina drilled a fierce 25-yard volley over.
Godin should have put Atletico ahead in the 20th minute, but he steered off target after meeting a free-kick delivery from deep.
And Lleida nearly capitalised shortly after - Miguel Angel Moya rushing out to deny Agudo from point-blank range after Molina's perfectly weighted through pass.
The breakthrough eventually arrived in the 33rd minute, as Godin rose highest to glance Yannick Carrasco's free-kick into the bottom-right corner.
Atletico's second shortly after was rather more impressive, however, as they won possession to the right of their own penalty area, patiently worked their way up the other end and Torres tapped in Kevin Gameiro's low cross.
Lleida began the second period much like the first and nearly pulled one back soon after the restart, but Agudo's header was kept out by Moya.
Simeone soon introduced debutants Vitolo and Costa, as well as Griezmann, with Atletico taking their foot off the pedal somewhat.
And Costa made a telling contribution 21 minutes from time, tucking in Juanfran's low cross and feeling the full force of a defender accidentally standing on his knee in the process.
But the Spain international managed to see out the rest of the game despite a nasty wound, as Atletico cruised and added a late fourth with a deflected Griezmann free-kick after Trilles tripped Gameiro just outside the area.