Spirit overcame feisty resistance from Eternal Fire while MOUZ pulled off a reverse sweep over G2.
The Counter-Strike 2 (CS2) ESL Pro League Season 21 Playoffs kicked off on Thursday (13 March) with its first two quarterfinal matches, where 
Team Spirit and 
MOUZ emerged victorious over 
Eternal Fire and 
G2 Esports, respectively, to become the first pair of teams to advance to the semifinals.
Both series took all three maps to decide a victor, with reigning Major champions Spirit overcoming feisty resistance from the side of Eternal Fire, while MOUZ pulled off a reverse sweep over G2 despite 
Ilya “m0NESY” Osipov's heroics. Here's how all the action in those two matches went down:
Spirit and MOUZ first to advance to ESL Pro League Season 21 semis
1-2
Team SpiritThe day started with a double overtime banger at Nuke, where Spirit zoomed to an early 7-1 lead as the T side behind a round 1 Ace from Leonid “Chopper” Vishnyakov and 1v3 clutch from Dmitry “sh1ro” Sokolov in round 7. However, Eternal Fire bounced back with four straight wins to trim Spirit's lead down to 7-5 by halftime.
The second half then saw Spirit go on a four-round streak and Eternal Fire answer with four straight of their own, only for the reigning Major champions to get within map point after round 21. However, Eternal Fire managed to string together three consecutive round wins to force the opening map of the series to overtime.
Eternal Fire won the first round of overtime as the T side but Spirit claimed the next two heading into the side switch. Eternal Fire then won back-to-back CT rounds to get on the verge of claiming Nuke, only for Spirit to lock in and dominate the next four rounds to secure the hard-fought 19-15 win. Chopper top-fragged for Spirit with 29 kills and eight assists on 20 deaths despite an illness, while 
Samet “jottAAA” Köklü had 31 frags and four assists against 23 deaths in the loss.
Map two at Anubis started with Spirit once again in control, winning three out of the first four rounds as the CT side. Eternal Fire then caught fire in round 5 and racked up 10 straight rounds into the second half to take a commanding 11-3 lead.
Spirit answered with a 7-1 run to threaten another overtime, but Eternal Fire deftly won round 23 to claim the 13-10 win in Anubis and force the series to a decider. Eternal Fire's win in Anubis was a notable team effort, with Can “XANTARES” Dörtkardeş, Engin “MAJ3R” Kupeli, and jottAAA all notching 16 frags apiece against 15, 14, and 10 deaths respectively.
Mirage hosted the deciding game of the series, where both sides went blow-for-blow and finished the first half tied at 6-6. Spirit then won the first two rounds of the second half as the CT side before a listless Eternal Fire could respond in round 15, following that up with five straight wins to secure Mirage with a 13-7 score and close out the 2-1 series victory.
Myroslav “zont1x” Plakotia led the way for Spirit in the closeout game with 16 frags and two assists on 10 deaths, while sh1ro added 14 frags and an assist on a server-best seven deaths.
2-1
G2 EsportsThe second series of the day saw MOUZ come back from an embarassing loss in the opening map to comfortably claim the next two and become the tournament's second semifinalist. M0NESY notably had yet another heroic performance to keep his team in contention, though it was not enough to get G2 to the semis.
The first map in Inferno started with G2 on the T side taking an early 3-1 lead before MOUZ went on a 6-2 run that gave them the 7-5 first half lead, even shaking off losing a 1v3 clutch to 
Nikita “HeavyGod” Martynenko, who scored two sneaky knife kills while under cover of a smoke grenade.
Both teams then traded the first four rounds of the second half until MOUZ won another two consecutive rounds to lead comfortably at 11-7. However, m0NESY and HeavyGod sparked a six-round streak for G2 that allowed them to steal the win at Inferno away from MOUZ with a 13-11 score. M0NESY led the way for G2 with 24 frags and three assists on 13 deaths while HeavyGod pitched in with 20 frags and four assists on a map-best 11 deaths.
MOUZ then bounced back in Nuke by winning the first five rounds as the T side, then fending off a 5-2 run by G2 to head into halftime with a two-round cushion. G2 looked like they could make another comeback after winning the first three rounds of the second half, but MOUZ completely shut them out with six straight wins to claim the 13-8 win at Nuke. Lotan “Spinx” Giladi notched 23 frags and three assists on 14 deaths to help MOUZ force the series to a deciding third game.
The series decider was at Ancient, where MOUZ looked dominant early on by winning seven of the first eight rounds as the T side. However, m0NESY and 
Nemanja “huNter” Kovač led G2 on a furious eight-round streak into the second half that gave them their first lead at 9-8. MOUZ won round 18 before more heroics from m0NESY and huNter allowed G2 to regain the lead at 11-9. But that was not enough to stop MOUZ as they closed out the series with four straight round wins to advance to the semifinals and send G2 packing.
Jimi “Jimpphat” Salo, Dorian “xertioN” Berman, and 
Ludvig “Brollan” Brolin all notched 19 frags in the closeout game for MOUZ against 12, 16, and 17 deaths respectively. Meanwhile, huNter and m0NESY put up admirable stat lines despite the loss with a combined 39 frags on 31 deaths.
With the day's results, Spirit and MOUZ advanced to the ESL Pro League Season 21 semifinals, securing at least a 3rd-4th place finish and US$25,000 in winnings. Meanwhile, Eternal Fire and G2 bow out in 5th-8th place and will each take home US$18,000 in consolation.
The second day of the ESL Pro League Season 21 Playoffs will feature the remaining two quarterfinal matches, with 
Team Vitality taking on 
Team Liquid, and 
Natus Vincere facing off against 
The MongolZ.
