Blades manager Neil Warnock made no fewer than ten changes to to side that beat Watford 3-2 at the weekend, with only captain Chris Morgan being the only player undisturbed.
Due to all these changes it allowed Midfielder Stephen Quinn and forward Gary Mulligan to make their first team debuts whilst Kyle McFarzden and Karl Nix later came off the bench to make their substitute debuts.
Jamie Annerson and Evan Horwood, who have yet to make starts for the Blades also made the bench but was not included throughout the duration.
The game itself was eventually won on a penalty shoot-out and despite Nix missing this spot kick the Blades sailed through with Shrewsbury keeper Joe Hart slamming his penalty into the woodwork.
In extra-time the tie steamed up as both teams pushed to end the game before each team had to take five penalty kicks. However this was rather unusual as the 90 minute game was rather boring to both supported fans and neutrals.
Soon into the start of the game United were targeted by a string of three attackers versus two lone defenders but Duanne Darby fired wide after McMenimen fed him through.
The Blades then responded with Michael Tonge who was introduced back into the squad after a four game albescence from the starting eleven opened up the visitors first chance when he put Danny Webber through to cross low before Alan Quinn's younger brother Stephen could reach it.
Replacement keeper Phil Barnes earned his loath six minutes in, Darby who looked busy early on in the game shot but Barnes dived right to palm away for a corner.
After a late challenge on former Wolves Winger Gary Mulligan, Tolley was cautioned where the following free-kick fell to Quinn who found his effort fire into a crowded box.
United were slow to get into the game but eventually as the visitors worked their way into the game created chances, Webber stabbed a shot wide whilst Keith Gillespie brought more into Midfield.
The Championship leaders did however win the majority of the possession with Town making sure there defence was kept tight, though played the counter-attack to a tea as Darby spurned two chances that he could do little with.
Town were awarded with the following shooting opportunity, Morgan failed to clear with a header which fell to McMenimen who found his 20 yard volley spin past the post.
HALF-TIME: SHREWSBURY TOWN 0-0 SHEFFIELD UNITED
At the break Town switched Mark Stallard for Darby who could have scored four within a short space of time. And, the former Barnsley and Chesterfield striker was soon in the thick of the action. A long ball confused Simon Francis as Smith slipped past him, a caution was issued to the defender after fouling Smith.
A free-kick taken by Herd hit Mulligan straight in the face as he got in the way but he resumed after treatment.
On 62 minutes Hart was called into action when he palmed Lilian Nalis header from a Gillespie corner over the bar.
And, of the United Midfield it was Quinn the younger who looked the most liveliest and his confidence rose minute-by-minute as his pot luck 20 yard shot went wide.
Seconds later, after recovering from a bang on the head Gillespie played the ball forward to Webber who jinxed past Hope where Hart covered well to thwart the ex-Watford strikers shot.
This, United's best move of the match sparked the Blades into life, captain Chris Morgan was denied by Hart from close-range while Gillespie lofted a ball too high for anyone to reach.
Town still attempted to create chances despite being pushed back, the Shrews forced Barnes into two good saves which spurred on the home crowed.
With four minutes left on the clock Francis saved the day for United as he cleared a vital shot which almost snuck underneath the crossbar.
FULL-TIME: SHREWSBURY TOWN 0-0 SHEFFIELD UNITED
The naturally went into extra-time with Town being more satisfied with the draw rather than the traveling United fans.
Former Aston Villa midfielder Karl Nix and McFadzean were allowed to make there debuts ands were quickly off the mark with Quinn being denied by Hart and his defence scuttled the ball away.
Frenchman Lilian Nalis floated in a lose ball which was headed by Quinn but failed to hit the target and the Irishman was denied a penalty when he was brought down in the box.
Mark Stallard beat the defence to fire at Barnes but it was the visiting side that had the upper hand.
Barnes caught a ball midway in the air and Rix twice had chances to dominate but both finishes were weak.
As apparel to being in defence McFadzean was cautioned on his debut for a challenge on McMenenimen as both sides went for it to avoid the dreaded penalties.
Little Alan Wright slashed his volley at goal but Hart turned the ball over the top, Tonge found his shot saved by Hart and Nalis fired the resulting rebound wide.
In the last seconds United tried desperately to book a place with the likes of Chelsea, Liverpool and Arsenal before penalties but were denied when Hart pulled off a World-Class save from Quinn.
FULL-TIME EXTRA-TIME: SHREWSBURY 0-0 SHEFFIELD UNITED
In the end it was seven shots and twelve yards that stood between cup glory and a waste of time. Geary, Wright and Marrison bulged the net whilst McMenamin and Sharp made it 3-2.
Stallard saw his shot fire over the top and Hart saved Nix penalty, Hogg made it 3-3 before man of the match Stephen Quinn netted. Town keeper Hart took their penalty which struck the cross to send United through..
:: Shoot-out sequences ::
0-1 Geary scores (bottom left)
1-1 McMenimen scores (bottom left)
1-2 Wright scores (top right)
2-2 Sharp scores (inside right post)
2-3 Marrison scores (inside left post)
2-3 Stallard misses, over top
2-3 Nix misses, saved
3-3 Hogg scores (bottom left)
3-4 Quinn scores, bottom left)
3-4 Hart (gk) misses, post