Tight end Saubert executed the game-winning two-point play for Seattle.
The Seattle Seahawks staged a remarkable fightback to overcome the Rams in overtime, clinching their place in the NFL play-offs.
Rallying from a 30-14 deficit in the final period, the Seahawks triumphed by a single point at home, registering their fifth straight victory.
While the Rams had already secured a playoff berth earlier on Sunday, the Seahawks secured their place to the postseason after a two-year hiatus.
With this result, the Seahawks have taken over their division's standings with a 12-3 mark, replacing the Los Angeles, who fell to the number five playoff position with an eleven and four record.
Signal-caller Darnold threw two picks but regrouped to deliver two touchdown passes, including the second TD to wideout Smith-Njigba in the extra period.
The visitors held a 13-7 advantage at half-time before Walker broke free for a 55-yard scoring dash for Seattle.
Los Angeles cornerback Josh Wallace then took back Darnold's first pick for a big return, leading to a one-yard score by Blake Corum on the next play.
In the final stanza, a scoring pass from Matthew Stafford to Nacua pushed the advantage to 30-14, but Rashid Shaheed provided the comeback with a spectacular punt return.
Darnold then connected with Barner in the endzone, and a successful two-point play sent the contest into overtime.
Although Nacua raced in for his second touchdown in OT, Jaxon Smith-Njigba responded in kind to set up the game-winning conversion.