Lakers' Wesley Johnson Sued -- VIOLENT REAR-ENDING ... Accuser Claims Severe Injuries

Just when you thought it couldn't get any worse for the Lakers ... small forward Wesley Johnson has been sued for allegedly slamming his BMW into another driver who claims she was seriously injured in the wreck.

TMZ Sports has learned ... the 27-year-old NBA player was hit with a lawsuit stemming over an August 14th crash -- when he allegedly rear-ended a Ford Focus on the 91 Freeway in L.A.

The alleged victim, Victoria Kane, claims Johnson was driving at a high rate of speed when he hit her -- sending the Focus across the HOV lane and into the highway median.

Kane claims she suffered multiple injuries to her head, face, shoulder, neck and arm -- and an ambulance transported her to a nearby hospital.

TMZ Sports obtained pics of Kane's car -- which was totaled in the wreck.

We reached out to Johnson for comment -- so far, no word back.