The ornamental design for a baseballswingtrainingdevice, as shown.
FIG. 1 is a perspective view of a baseball swing training device according to a first embodiment of our new design;
FIG. 2 is an alternative perspective view thereof;
FIG. 3 is a side view thereof;
FIG. 4 is a proximal end view thereof;
FIG. 5 is a distal end view thereof;
FIG. 6 is a perspective view of a baseball swing training device according to a second embodiment of our new design;
FIG. 7 is an alternative perspective view thereof;
FIG. 8 is a side view thereof;
FIG. 9 is a proximal end view thereof; and,
FIG. 10 is a distal end view thereof.
Features shown in dashed lines form no part of the claimed design. Although a portion of the grip area of the device is shown in dashed lines on the shaft, the shaft extends between the grip end and the barrel end of the device.