Steelsplitter is a versatile unit that can build pressure against the opponent or defend. However, Steelsplitter is less efficient than other Base Set units at both of those tasks: it costs 1 more than a Wall and isn't Prompt, and 2 more than a Tarsier for the same attack. As a consequence it is usually incorrect to plan on having Steelsplitters as your main attackers.
The first player to build a Blastforge in the early game will often have the opportunity build a Steelsplitter for early pressure, forcing the opponent to respond with a prompt defender to avoid losing an Engineer. Here is a typical opening play illustrating this:
- DD, DD
- DD, DDC
- DDB, DDB
- DDS, DDW
Buying Steelsplitter in this context is justified due to its versatility: it puts attack, and it may defend if your opponent suddenly threatens damage, or if you buy a big blue unit after it such as Omega Splitter and don't need a Wall yet. Again, later in the game, buying Steelsplitter simply for additional pressure is not the most efficient, but if the choice is between that and wasting blue, it is probably best.