A powertrain is disclosed. A ring gear is attached to a first distal end of a crankshaft such that the ring gear and the crankshaft are rotatable in unison about a longitudinal axis. A motor-generator includes a motor/generator shaft rotatable about a first axis spaced from the longitudinal axis. A starter mechanism includes a first starter gear coupleable to the motor/generator shaft and rotatable about a second axis spaced from the longitudinal axis. The first and second axes are spaced and substantially parallel to each other. The first starter gear is movable along the second axis between a first position engaging the ring gear such that torque is transferred from the motor/generator shaft through the first starter gear and the ring gear to the crankshaft to start the engine, and a second position disengaged from the ring gear to rotatably disconnect the starter mechanism from the ring gear.