Favorites BIG and Cloud9 each won close quarterfinal battles on Monday, becoming the first two teams to claim semifinal berths at the Roobet Cup.

Group B winner Cloud9, which went 2-0 and posted an event-best plus-30 scoring differential in the group stage, advanced by the thinnest of margins in a 2-1 nail-biter over 9z Team. BIG, the Group A champion at 2-0, also needed three maps to take out Eternal Fire 2-1.

Monday's results paved the way for a head-to-head semifinal clash on Wednesday between BIG and Cloud9.

The top two teams from each group advanced to the single-elimination playoffs, where matches are best-of-three. The winner of the $250,000 Counter-Strike: Global Offensive event will earn $150,000, with the grand final scheduled for Thursday.

After smooth sailing through the group stage, Cloud9 found themselves trailing 11-6 in the opening map on Mirage before rallying for a 16-13 win. 9z Team responded by handing Cloud9 their first map loss of the event, a 16-10 decision on Dust II, to tie the match. The decisive map went down to the wire, with Cloud9 pulling out a 16-14 triumph on Overpass.

Dmitry "sh1ro" Sokolov of Russia led Cloud9 with 61 kills and a plus-17 kills-deaths differential. 9z Team was carried by Uruguay's Maximiliano "max" Gonzalez, who recorded a match-high 64 kills along with a plus-12 K/D differential.

BIG also fell behind early in their clash with Eternal Fire, trailing 7-4 early before rattling off 12 of the final 15 points on their first map to win 16-10 on Overpass. BIG then built a seemingly insurmountable 12-1 lead on Dust II, but Eternal Fire roared back for a stunning 19-16 overtime thriller. With the match at 1-1, BIG corrected course with a 16-7 clincher on Nuke for the victory.

Florian "syrsoN" Rische led BIG's all-German lineup with 69 kills and a plus-18 K/D ratio. For Eternal Fire, Bugra "Calyx" Arkin topped the all-Turkish unit with 64 kills and a plus-13 K/D differential.

Two quarterfinal matches are scheduled for Tuesday:

--ENCE vs. FaZe Clan

--forZe vs. Astralis

Roobet Cup prize pool:

1. $150,000 -- TBD

2. $50,000 -- TBD

3-4. $15,000 -- TBD

5-8. $5,000 -- Eternal Fire, 9z Team, TBD, TBD

9-12. no money -- OG, Complexity Gaming, MOUZ, FURIA Esports

13-16. no money -- Entropiq, Movistar Riders, Imperial Esports, Outsiders