The visitors – second bottom of the Championship and without their two leading lights in batsman Marcus North and seamer James Harris – might have been expected to roll over meekly against a side expected to gain promotion.
But after winning the toss and electing to bowl (an interesting decision given that the ground was bathed in glorious sunshine), Yorkshire did not break through until 20 minutes into the afternoon session, much to the palpable relief of their players and supporters.
Will Bragg and Nick James, 25-year-old left-handers both, frustrated Yorkshire with an opening stand of 124, which eclipsed Glamorgan’s previous first-wicket best in the Championship this season – the 75 added by Bragg and Gareth Rees against Leicestershire at Cardiff in May.
However, from the moment that James drove at a wide ball outside off stump from Ryan Sidebottom and was caught behind by Andrew Hodd, the soft underbelly of the Glamorgan batting was gradually exposed.
A Yorkshire attack that was not quite at its collective best did not need to be as the visiting side were steadily pegged back.
Steve Patterson took 4-49 (how on earth did he not feature in Yorkshire’s end-of-season player awards?) and Sidebottom, Anthony McGrath and Azeem Rafiq claimed two wickets apiece as Glamorgan – at one stage 221-4 – were ejected for a mediocre 272.
Yorkshire safely negotiated six overs before stumps to end the day a good deal happier than had earlier seemed likely.
Following their dramatic two-wicket victory against Gloucestershire at Scarborough, which consigned the West Country side to the foot of the table in Glamorgan’s place, Yorkshire made one change as Sidebottom was recalled following a back injury in place of leg-spinner Adil Rashid.
The former England man bowled an economical opening spell of 0-17 from six overs but there did not appear to be a great deal in the pitch, despite its somewhat greenish tinge.
Full-length balls seemed the best way to go and there were one or two grumbles among a good-sized crowd as Yorkshire initially struggled to back-up their decision to bowl.
Bragg and James brought up the fifty stand in 70 minutes, the former the more aggressive of the pair, and it was only when Patterson came on for a second spell from the Kirkstall Lane end just before lunch that the openers appeared unduly concerned.
Patterson went past the bat on several occasions but it was Rafiq who created the only clear-cut chance of the morning session, Adam Lyth spilling a tough opportunity moving to his left when James, on 16, edged to slip.
Bragg went to an 83-ball half-century by carving Rafiq through mid-wicket for four and then repeated the feat during an over in which he also square-cut the spinner to the boundary.
Before that, Rafiq had bowled seven tidy overs for 10 runs, a parsimonious performance which forced the batsmen to rethink their strategy.
Glamorgan lunched on 103-0 but Yorkshire hit back during an afternoon session in which they claimed four wickets for 86 runs.
After Sidebottom got rid of James, Bragg was next out on 140 when he fell eight runs short of what would have been a deserved century, nibbling at a ball from Patterson which he nicked to Hodd.
Patterson struck again when David Lloyd, a 20-year-old right-hander making his first-class debut, was caught behind off an attempted off-drive, and Glamorgan would have slipped to 175-4 but for an uncharacteristic blunder by Gary Ballance.
When Stewart Walters, on 31, edged McGrath to first slip, Ballance grassed a simple chance – something of a Sod’s Law moment considering that, two days earlier, the 22-year-old had been named Fielder of the Year at Yorkshire’s end-of-season player awards.
In the very next over, Walters had another life when Hodd spilled him off Rafiq, but the damage was minimal as the spinner removed him shortly afterwards for 42, splendidly caught by Lyth at slip, diving to his right.
Jim Allenby got off the mark with a straight six over long-on off Rafiq but Glamorgan’s middle and lower-order steadily crumbled.
Three wickets fell in 20 balls as Sidebottom had Ben Wright lbw before McGrath had Allenby caught behind and then bowled Graham Wagg as the visitors slid to 223-7.
Patterson bowled John Glover for a duck, Rafiq had Mark Wallace superbly caught by Phil Jaques at short-leg and the innings ended when Patterson had Dean Cosker caught behind.
Lyth and Joe Root gave Yorkshire’s innings a solid start, moving to 20-0, with Root’s fleeting appearance ensuring that National Selector Geoff Miller’s visit to Headingley was not entirely in vain.