On January 29th, Valve released an update with several changes to competitive maps, specifically 3 maps: Dust2, Train, and Mirage. Dust2 and Train had their skybox opened in the B Tunnel and Ivy areas, while the changes to Mirage included the addition of a chair in the mid area for the T-Side to boost up to window and peek B-short, along with the top mid area being expanded towards T-mid.
All three maps are part of the official competitive map pool of CS:GO and are used in all major tournaments worldwide, so pro players – those directly affected by it – have shared their thoughts on these changes.
Dust2
Most players agree that this change benefits the T-side as they can now throw flashes/smokes from inside the Tunnel to cover important positions like window or B door, while the CTs will have to play 2 players at B to secure this bombsite against the opponents’ attacks.
EliGE (Team Liquid): “I think this is the most confusing change because avoiding being blinded by the opponent’s flashes is already difficult, and now the opponent can set up plays from the tunnel area with crazy flashes; holding B will be nearly impossible.”
NIKo (FaZe Clan): “Now you’ll need to find a way to prevent B bombsite plays. This will be the biggest change.”
kennyS (G2 Esports): “Opening the skybox in Dust2 creates many new possibilities, and I believe changes are always a good thing. We might witness some truly impressive plays in the near future.”

apEX (Team Vitality): “I think aside from the flashes, Dust2 won’t change too much; the smokes at B will be easy to counter, but the flashes will be very effective in setup, rushing, or retaking situations. Both sides will benefit, and I feel quite happy with this change.”
Train
Similar to Dust2, many pro players believe this will be a significant change that impacts the strategies of both sides.
NIKo (FaZe Clan): “This is truly a fantastic change and it will help balance the power between the sides, no longer skewed as it was before.”
Brehze (EG): “This change is quite nice and I really like it. As a player playing in Ivy, I can now support my teammates from this area with smokes and flashes.”
Karrigan (Mousesports): “Opening the skybox in Ivy is a reasonable change. What I like most is that both sides benefit from this change. CTs can control Ivy more easily with a smoke from Z Connector, for example. It might lean slightly towards the T-side, but for a map like Train, that’s necessary since it’s known to favor CTs too much.”

Mirage
This map has the most changes as the design team added a chair in the Mid – Connector area, expanded the mid area from the T side, lowered the Balcony area from B, and removed the jump check trick from B-site to B-short. All these changes benefit the T-side, and most pro players share this view.

blameF (Complexity): “The addition of the chair in the mid area will change a lot of timings between the middle and end of rounds, but overall I don’t think there will be too many changes since CTs will always be present in Connector, Window, or Short at the start of the round. Perhaps in clutch situations or 2v2s at the end of the round, CTs will need to be careful of players flanking from behind.”
jkaem (100 Thieves): “The chair in Mirage is really a stupid change, and I believe every other pro feels the same. Everyone talks about jumping into window early and flanking CT players; that’s obviously true, but the problem is you’ll make noise. After practice sessions, I don’t see any changes at all. The only point is that players in B-short will be easier to take down than before. Right now, no one is using this chair effectively, but who knows what the future holds.”
EliGE (Team Liquid): “This is definitely a disadvantageous change for CTs. Previously, moving around on this map was already difficult, and now you’ll have to be constantly aware of the Window area. The opponents can easily jump into Window and then into Ladder room, suddenly appearing at B-short, and CTs will always have to be alert about this.”

kennyS (G2 Esports): “I actually like the chair in Mirage because it allows me to get into window by myself. It brings many new possibilities, and let’s wait for what the future holds.”
karrigan (Mousesports): “I really don’t understand why they lowered the Balcony area. Previously, players jumping to check B were already easy targets for AWPers, and with this change, B players will really struggle. As for the chair in mid, while playing in B short will be harder, it will also bring new changes to the game and even change the meta. People will need more time to get used to it.”
These unusual changes will surely bring a fresh breeze to the professional CS:GO scene and give IGLs/Coaches the chance to showcase new strategies of their own. Hopefully, in the upcoming LAN events, we will witness top teams employing unique strategies surrounding these changes.