A logical move, which has the idea of ​​playing a3 and then taking with the knight on c3.
1. d2d4  1... g8f6  2. c2c4  2... e7e6  3. b1c3  3... f8b4  4. e2e3  4... b7b6 Less played than 4...0-0 or 4...c5, but still with a gigantic theory, like all the lines of this classic Nimzo-Indian line.