We present a high-rate $(n,k,d=n-1)$-MSR code with a sub-packetization level that is polynomial in the dimension $k$ of the code. While polynomial sub-packetization level was achieved earlier for vector MDS codes that repair systematic nodes optimally, no such MSR code construction is known. In the low-rate regime (i. e., rates less than one-half), MSR code constructions with a linear sub-packetization level are available. But in the high-rate regime (i. e., rates greater than one-half), the known MSR code constructions required a sub-packetization level that is exponential in $k$. In the present paper, we construct an MSR code for $d=n-1$ with a fixed rate $R=\frac{t-1}{t}, \ t \geq 2,$ achieveing a sub-packetization level $α= O(k^t)$. The code allows help-by-transfer repair, i. e., no computations are needed at the helper nodes during repair of a failed node.