Champions League: Luis Suarez, Joao Felix key to unlocking Chelsea defense, says Atletico Madrid's Diego Simeone
"Only one objective: victory," said Simeone, whose team face a 1-0 deficit in the last-16 tie after losing their 'home' game in Bucharest. "I must find the necessary tools to achieve this."
Lemar and Herrera join Mario Hermoso, Joao Felix and Moussa Dembele on a list of five Atletico players currently out after contracting the illness. Atletico have been hit hard by the virus, with eight players previously having tested positive besides coach Diego Simeone.
"Joao Felix has tested positive for COVID-19. The striker is isolating at home, in compliance with the health authorities' guidelines and La Liga protocols," Atletico said in a statement.
LaLiga: Atletico Madrid come from behind to beat Valencia 3-1; Barcelona down Elche 2-0 without suspended Lionel Messi
Coming from behind for a second straight time, Atletico defeated Valencia 3-1 on Sunday to strengthen their hold on the league lead entering the second half of the season.
Dembele will join Atletico until the end of the season when the club will have the option to buy him permanently for around 35 million euros.
A first league victory over Barca since 2010 would put Atletico nine points clear of their opponents and extend an impressive unbeaten run in the league to 24 matches.
LaLiga: Unbeaten Atletico Madrid take top spot; Lionel Messi rescues Barcelona off the bench as Ansu Fati suffers injury
While Messi got Barcelona back on track, Joao Felix’s latest double helped Atletico Madrid rise to the top of the league with a convincing 4-0 rout of Cadiz.
LaLiga: Real Betis climb to top of league table with win over Valencia; Villarreal hold Atletico Madrid to goalless draw
Atletico Madrid struggled again with Luis Suarez in attack, and were held by Villarreal for their second straight 0-0 draw. Meanwhile, Eibar claimed a 2-1 victory over Valladolid.
Champions League: Tyler Adams' late strike sends RB Leipzig to their first semi-final after victory over Atletico Madrid
Leipzig's challenge is now to defeat PSG on Tuesday, the French champions who have only played three matches in almost half a year and needed a late escape to see off Atalanta on Tuesday
LaLiga: Joao Felix scores twice as Atletico Madrid end winless streak with comfortable victory over Osasuna
Joao Felix scored twice in his first match back from injury as Atlético Madrid routed Osasuna 5-0 on Wednesday to end their winless streak and regain fourth place in the Spanish league.
LaLiga: Atletico Madrid's Joao Felix likely to miss resumption of season after picking up knee injury in training
Atletico said in a statement the 20-year-old, who cost the club 126 million euros ($137.31 million) from Benfica last year, had sprained the medial ligament in his left knee.
LaLiga: Joao Felix marks return from injury with goal to help Atletico Madrid beat Villarreal; Alaves best Athletic Bilbao
Substitute Joao Felix returned from injury and scored his first goal in more than two months to help Atletico Madrid get back in the fight for a Champions League berth on Sunday.
Champions League: Once leaders in player conditioning, Atletico Madrid wrestle with injury crisis as Liverpool visit
Compared to an all-powerful Liverpool side on course for a record-smashing Premier League title triumph, Atletico Madrid certainly look vulnerable
LaLiga: Atletico Madrid striker Alvaro Morata sidelined with muscle injury as club's forward crisis deepens
Morata suffered the injury during the 1-0 derby defeat by Real Madrid on Saturday which left his side sixth and 13 points behind their rivals who are top of La Liga.
Spanish Super Cup: Alvaro Morata, Koke on target as Atletico Madrid battle past Barcelona to set up finale against Real Madrid
Atlético Madrid rallied with two late goals to beat Barcelona 3-2 in a back-and-forth game on Thursday, setting up a meeting against city rival Real Madrid in Sunday's final at the revamped Spanish Super Cup.
Atletico stayed in sixth place with 26 points from 16 matches, five points behind leaders Barcelona and Real Madrid, which both have two games in hand on Atletico entering the weekend — including one against each other on 18 December.
LaLiga: Forward Joao Felix awarded 2019 Golden Boy for stellar performances with Atletico Madrid, Benfica
Felix became the youngest player to score a Europa League hat-trick in a 4-2 win over Eintracht Frankfurt last season and helped the Lisbon side win the Portuguese league title with 15 goals and seven assists in 21 starts
LaLiga: Alvaro Morata nets his sixth goal in all competitions as Atletico Madrid come from behind to defeat Espanyol
Morata thumped home his fifth league goal of the season just before the hour mark to put Atletico in front in Madrid after Sergi Darder had shocked the Wanda Metropolitano with fine opener seven minutes before the break.
LaLiga: Atletico Madrid hope to turn 'whistles into applause' in Athletic Bilbao fixture after hat-trick of draws
Diego Simeone’s Atletico Madrid are aiming to turn jeers into cheers on Saturday against Athletic Bilbao after three consecutive La Liga draws.
Barcelona sailed back to the top of the table on Saturday and trouble returned to Real Madrid after they endured their first LaLiga defeat of the season at newly-promoted Real Mallorca.