Worker Scout with Gas First Opening

I have seen many strong comments on forums regarding not sending a worker to scout for gas first opening. While I can agree with it to a certain extent, I think there is more to it than just an absolute yes or no.


The idea of not scouting in the early game can be beneficial may seem counter-intuitive to newer players, as others always shout loudly how important it’s to scout. However, gas first opening seems to be one of the exceptions that perhaps scouting is not that rewarding. There are generally two reasons why early worker scouting is unnecessary. First, it is the inability to make use of the information. A good example will be a proxy two Barracks cheese. It is almost certain that you will continue to execute your build no matter you see if you do a standard worker scout, so you rather have the scouting worker mining instead. This leads to the next reason, second, it is the opportunity cost of scouting. Some builds are very extreme, like a proxy two Barracks cheese, and they require every bit of the mineral.

Just to be clear before I continue. “Worker scout” in this case refers to sending a worker to opponent’s base to gather information about opponent’s build. That means, it does not include scouting for opponent’s spawning location. It is normal to do minimal scouting with a proxy two Barracks to deduce opponent’s spawning location.

For more information of basic scouting, read this.

The question and answer

Are the two reasons applicable in the gas first opening to justify not scouting?

My answer is “yes, but…”

There are quite a number of gas first builds, and there is room for changes. Let say in TvT, there are two main streams of gas first openings: single or double gas. Single gas is usually Hellion, Marine and Medivac based attack, while double gas is usually Banshee or Raven. I doubt a standard worker scout can provide information whether to take the second gas or not, unless you know opponent is doing a proxy cheese. However, a standard worker scout may be able to gather information that can influence your decision on what unit to get and unit positioning. For example, if you scout that opponent is going for the same gas first with double refineries build as you do, then it is better to get a Raven than a a Banshee. This is because if one player gets a Raven and the other gets a Banshee, the Raven player usually has an upper hand. Another example, if you scout that opponent is going for the same gas first with single refinery build as you do, then it may be better to go for two Hellions and a Widow Mine instead of three Hellions. This is because it allows you to attack with six Marine and a Widow Mine, while you have the Hellions in base to defend opponent’s attack.

The vod below is a game between Dream and Maru in the KeSPA Cup. Both went for gas first six Marine, two Hellions, one Widow Mine and one Medivac build (just a different production sequence from the Factory). Maru scouted with a Scv early on, and decided to leave his Hellions in base to defend while he attacked with his drop. In contrast, Dream did not do a Scv scout in the normal timing, but he did something brilliant to make up for it. He sent his Scv to scout at the perfect timing to spot Maru’s build, after he deduced that Maru wasn’t doing a Reaper opening. Dream immediately pulled his Hellions back to defend, while he sent his drop to attack. Thus, based on this, there seems to be a consensus in how to play out this build interaction. But the point is, if Dream’s delayed Scv scout was denied, which was extremely likely, Maru would have played out the build interaction better due to the Scv scout. Therefore, the first reason (inability to make use of the information) is not exactly true.

Personally, I find the second reason a little bit weak, because it can sort of applied to almost every build. It basically delays the build by a few seconds, since you will have to wait for the mineral to put down certain buildings (you will know if you play gas first builds). Of course, all else equal, you don’t want to delay a second if possible. The thing is whether the benefits of the information gathered from scouting  outweigh the slight delay. It is hard to give a simple answer for this.

I collected some TvT data from Proleague playoff, Season 3 GSL and SSL (No TvT in SSL).

Untitled-1Some key take away from the data.

  • No Scv scout on two player map
  • Scv scout on four player for spawn location
  • If you scout, send the Scv after the Barracks is completed

If you only look at the data in the recent games, the answer seems to be quite clear. You don’t scout with gas first build. However, if you look at the games played earlier this year, there will be Scv scout with gas first. The vod above is a good example, and the game was played in the KeSPA Cup between Season 2 and 3. I am too lazy to gather more data, but I am quite certain that there are even more games last year that you can find Scv scout with gas first. I cannot give a conclusive reason, but I speculate that it is due to the metagame. Last year, the metagame is mainly gas first openings, and it’s only a matter of what build you choose. As I have explained earlier, the two general reasons to not worker scout are kind of weak in gas first mirror builds. Of course you don’t know what opponent is going to do for sure, but it is relatively more rewarding to scout if there is a good chance opponent is going for gas first too because of the metagame understanding. Another notable difference is the development and popularity of defensive gas first Reaper opening, which allows you to scout well beyond the usual worker scout period.


It is fair to conclude that it is optional to worker scout if you go for gas first, and it is preferred in maps that you don’t know your opponent’s spawn location.

There are other considerations, like whether opponent sends a worker to your base. If s/he does, does that mean that it’s less likely s/he is doing a gas first build?

Clearly, the builds will be different in Legacy of the Void, but the two reasons for not worker scout are applicable. Thus, the thinking process of analysing the merits of whether to work scout of not should be very similar in Legacy of the Void.

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