The surprise was there was no surprise. Or maybe the surprise was that, after such a remarkable weekend, the bigger club wasn't humbled. West Bromwich had looked the most vulnerable of the more renowned quarter-finalists but, instead, are on course to complete a remarkable double-double having been the last club, in 1931, to win promotion and the FA Cup.
But, for an hour, how they were pushed. Rovers turned up the Gas in a pulsating, joyful tie as they attempted to reach the semi-finals for the first time in their own, less illustrious history. No neutral would have begrudged them that given the crackling positivity of their football and their relentless commitment, although neither would anyone deny that West Bromwich, too, are full of wonderful attacking intent.
Unusually both clubs went into this tie, with the prize of a semi-final at Wembley, having already played at the new stadium.
Last season, while Rovers won promotion to League One, West Brom were defeated in their attempts to make an immediate return to the Premier League. Although that remains the goal this season, manager Tony Mowbray's selection showed an awareness of what was at stake although there may have also been a tinge of apprehension with the threatening storm clouds and the blistered pitch.
The match was also played at a blistering pace. Rovers created a flurry of opportunities with Leon Barnett having to hook away a dangerous cross by Aaron Lescott before Craig Disley's swivel and shot cleared the crossbar.
But they were then quickly two goals down. The power and pace of West Brom's strikers was too much while goalkeeper Steve Phillips appeared gripped by nerves. He failed to push Roman Bednar's shot far enough away from goal and the ball slid to James Morrison who gleefully hammered it into the net. Earlier Phillips had been fortunate to escape as he hesitated when Ishmael Miller ran through, only to eventually push out the header and then see Jonathan Greening's drive strike him. But he was rooted to the spot as, moments later, Miller powered past Joe Jacobson and thumped in a swerving shot from 20 yards which appeared to kill the contest.
Not that Rovers were having it as they pulled a goal back just seconds later.
Stuart Campbell's corner was headed on for Danny Coles to beat Dean Kiely with a low shot. It was the least their committed, enterprising play deserved. As half-time approached Campbell's curling shot drifted narrowly wide with Kiely scrambling.
Into the second-half and Phillips was again flapping but somehow deflected Bednar's header before Craig Hinton hacked off the line.
Miller then wildly sliced his shot when put through from Robert Koren's clever reverse pass. Not that Rovers were fazed. They upped the pace and four half-chances went begging.
Then, cruelly, West Brom scored. A woeful header back towards his own goal by Hinton fell to Miller. He would have been yards offside if a team-mate had passed to him but he turned and slipped a low shot under Phillips to stun the home supporters. Soon after substitute Kevin Phillips added another, tucking the ball crisply into the corner of the goal after it rebounded off Miller's from Greening's through ball. It ended any doubts even if Lewis Haldane struck the inside of the post before Miller completed his hat-trick, calmly side-footing home from a pull-back.
Goals: Morrison (16) 0-1; Miller (30) 0-2; Coles (31) 1-2; Miller (69) 1-3; Phillips (73) 1-4; Miller (85) 1-5.
Bristol Rovers (4-4-2): Phillips; Lescott, Hinton, Coles, Jacobson; Pipe (Walker, 72), Campbell, Disley, Lines (Haldane, 55); Williams (Igoe, 81), Lambert. Substitutes not used: Green (gk), Anthony.
West Bromwich (4-4-2): Kiely; Hodgkiss, Albrechtsen, Barnett, Robinson; Morrison (De-Heon, 84), Greening, Koren, Brunt (Gera, 63); Bednar (Phillips, 63), Miller. Substitutes not used: Danek (gk), Pele.
Referee: M Clattenburg (Tyne & Wear).
Man of the match: Miller.