SUNDERLAND'S relegation fears intensified as they crashed to a 2-0 defeat at the hands of relegation rivals Norwich City.
With Fulham, Cardiff, West Brom and Crystal Palace all losing, Sunderland remain three points adrift of safety but, significantly, they now find themselves seven points behind Norwich, who have done much to aid their own chances of avoiding the drop in recent games.
There was little they could do about Tettey's goal in particular, with the midfielder producing a contender for Goal of the Season as he rifled home a volley.
But their display was still alarmingly short of desire and urgency given the significance of the occasion and their perilous position in the bottom three.
There was also a sting in the tail right at the death as Marcos Alonso was dismissed when he picked up a second yellow card for deliberate handball.
Gustavo Poyet made two changes to the side that had drawn with Crystal Palace seven days earlier, with Jack Colback replacing Seb Larsson in midfield and Jozy Altidore coming into the side for the injured Steven Fletcher.
The importance of the game to both sides was obvious given their positions in the bottom half of the table, but while Norwich's players were clearly fired up from the outset, Sunderland were lethargic throughout the first half.
While Snodgrass and Jonny Howson were snapping into tackles in midfield, the Black Cats were hesistant and lacklustre, showing little in the way of commitment or urgency.
They might have fallen behind in the 12th minute when Howson's shot deflected off Wes Brown, but while Vito Mannone was able to save on that occasion, he was unable to do anything when Norwich threatened again eight minutes later.
Brown was involved again, producing a weak defensive header from Martin Olsson's cross that fell straight at the feet of Johan Elmander.
The Swede squared the ball across the face of the area, and Snodgrass calmly slotted home with a crisp first-time finish.
Norwich were the dominant side throughout a one-sided first half, and Mannone was forced into a decent save in the 25th minute to keep out another smart effort from Howson.
A second goal looked on the cards though, and it dully arrived in spectacular fashion 12 minutes before the interval.
John O'Shea produced a decent header to clear Wes Hoolahan's left-wing cross, but without breaking stride, Tettey drilled a sensational first-time volley into the bottom right-hand corner of the net.
The midfielder was 25 yards out when he took aim, but the ball screamed past Mannone, who had no chance of keeping it out.
Poyet's response was an immediate double change, with Lee Cattermole and Seb Larsson replacing Ki Sung-Yueng and Jack Colback.
The ploy at least gave Sunderland some increased attacking initiative, and Fabio Borini finally forced John Ruddy into his first save of the game when he latched on to a knock down from Jozy Altidore and drilled a low strike across the goal.
Poyet's half-time team talk will have contained plenty of strong language, and Sunderland's players were back on the field a full five minutes before the restart.
However, the pattern of the game remained unchanged at the start of the second half, with Mannone having to produce an excellent save to tip Ricky van Wolfswinkel's stooped header over the crossbar.
Two minutes later, and Ruddy matched him with a save that was every bit as good. Brown met Adam Johnson's left-wing cross on the edge of the six-yard box, but Ruddy produced an fine reflex stop to keep out his close-range header.
To be fair to the Black Cats, their second-half performance was a considerable step up from the tepid fair they produced before the break, with Cattermole's midfield urging and obvious desire for the ball spreading through his team-mates.
They still struggled to create chances though, and Poyet made his final change with 19 remaining as Ignacio Scocco replaced Johnson.
The Black Cats would have had a three-goal deficit to attempt to overhaul had Mannone not got down well to save Hoolahan's low effort However, there was still a final setback as Alonso, who had already been booked in the first half, was dismissed in stoppage time when he handled the ball in the Norwich area from a corner.
NORWICH (4-4-1-1): Ruddy; Martin, Yobo, Bassong, Olsson; Snodgrass, Howson, Tettey, Hoolahan (Redmond 89); van Wolfswinkel (Hooper 71); Elmander (Johnson 87).
Subs: Bunn (gk), Whittaker, Gutierrez, Becchio.
SUNDERLAND (4-1-4-1): Mannone; Bardsley, Brown, O'Shea, Alonso; Bridcutt; Johnson (Scocco 71), Ki (Cattermole 39), Colback (Larsson 39), Borini; Altidore.
Subs (not used): Ustari (gk), Celustka, Vergini, Giaccherini.