As a Starcraft 2 Terran player, you are very susceptible to early game rushes. If Zerg or Protoss is rushed it may result in losing a few workers, whereas when you are rushed it could mean losing the game. Marines are pretty flimsy, so you have to do your best to protect them with what you have early in the game.
Many newer players will probably feel most comfortable completely walling off the entrance to their base when up against Zerg players. This way if they send early Zerglings, they will be stuck attacking your Supply Depots while your Marines fire on them with impunity.
But there are other ways that Zerg can rush too. Here are 4 different rush strategies and how to spot them when you scout in a Terran vs Zerg matchup. Zerg doesn’t have any way to proxy, and I haven’t seen a strategy for an early Hatchery + Spine Crawler push yet. So get your scout into their base early to see what they are up to.
This strategy has been around since the early days of the original Starcraft, catching unsuspecting players with no defenses and taking early wins. If their Spawning Pool is already up or almost done when you get your scout in their base you better bet that there’s going to be some early Zerglings to your base. To fight this off finish your wall off quickly and get a Marine out to push them back so they can’t kill your buildings.
This strategy isn’t as popular as it was in beta when Roaches were only 1 supply. If your scout sees the Spawning Pool up and one gas being mined, then wander around his base for awhile to see what he’s up to. If an early Roach Warren gets put down you’ll have to tech up to Marauders to keep them at bay.
A little more popular is the Zergling to Roach transition. The Zerg player will start off with a ton of Zerglings and bait you to get a lot of Hellions and Marines. Then he will quickly transition to a big Roach force that will handily take out your force and destroy your base, so watch out for it!
Banelings are extremely dangerous and will take out Supply Depots and Marines really fast. If your scout sees that a Baneling Nest has been built, then you need to reinforce your wall. Just a few Banelings will take out a Supply Depot then you could have a bunch of Zerglings streaming into your base through the hole. Getting some early Hellions to roast them and Marauders to stand in front of your Marines can help you fend off an early Baneling Bust.
If your scout gets into your opponent’s base and see 2 gas Extractors put up, then there’s a good chance that he’s going to do a 1 base Mutalisk rush. After he gets the Spawning Pool he’ll immediately upgrade to a Lair and put a Spire down. You’ll need a lot of Marines and/or Thors to fight off Mutalisks. Tech up quickly and keep scouting to be sure that’s what he’s going for.