Receiver Saubert made the game-winning two-point play for Seattle.
Seattle engineered a remarkable comeback to overcome the Rams in overtime, clinching their place in the NFL play-offs.
Overcoming a 30-14 deficit in the final period, the Seattle squad emerged victorious by a single point at home, registering their fifth straight win.
While the Los Angeles had become the first to earn a post-season spot earlier on game day, the Seahawks booked their return to the play-offs after a two-year absence.
With this result, the Seahawks have taken over their division's standings with a 12-3 mark, supplanting the Rams, who fell to the fifth seed with an 11-4 record.
Quarterback Darnold threw two picks but recovered to make two touchdown passes, including the second TD to wideout Jaxon Smith-Njigba in the extra period.
The visitors held a 13-7 advantage at the break before Walker broke free for a 55-yard touchdown run for Seattle.
Rams cornerback Wallace then took back Darnold's first pick for a big return, leading to a one-yard touchdown by Blake Corum on the ensuing snap.
In the fourth quarter, a scoring pass from Matthew Stafford to Nacua pushed the Rams' lead to sixteen points, but Rashid Shaheed provided Seattle's comeback with a spectacular punt return.
Darnold then connected with AJ Barner in the end zone, and a converted two-point play sent the game into overtime.
Although Puka Nacua raced in for his another touchdown in OT, Smith-Njigba responded in kind to setup the game-winning conversion.
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