Stuttering Rovers are in danger of a fourth successive defeat which could yet see their play-off place jeopardised.
Beset by injuries, they fell 38-20 at home to Hull FC on Sunday despite leading at half-time.
“In the first half we bombed three or four tries and we really need to take those chances,” said Sandercock.
“The real top sides do take them and we need to be a bit more composed.
“That would be a big improvement at Leeds.
“They’ve got some guys in (Rob) Burrow, (Kevin) Sinfield and (Ryan) Hall who can really hurt you themselves so we need to limit their opportunities.
“It (injury situation) is unprecedented. On the weekend we were missing our entire starting forward pack except for our hooker so to compete against a side that spends an awful amount of money on its roster was pleasing.
“You’d have to be brave person to pick us (at Leeds) but as long as the boys believe they can win, play at their best and execute game plan you never know what can happen.
“The longer you can hang in against these big sides the more they can get a little bit nervous and you never know what can happen.”
Rovers – who have slipped to eighth and could yet be overhauled by Bradford Bulls if they do not emerge from their rut soon – should be helped by the return of Australian hooker Lincoln Withers after suspension.
Back-row Rhys Lovegrove is hopeful of a return too after frustratingly pulling up in the warm-up against Hull.
“He’d been carrying a sternum/rib injury but the medical staff were pretty confident with a painkiller he’d be able to get through,” explained Sandercock.
“But the painkiller didn’t work – which does happen sometimes – and he couldn’t start the game.
“He needs to (get back) as we’re down to the bare minimum of bones now. He needs to step up.”
The visitors have lost dynamic full-back Greg Eden to a season-ending knee injury.
“He’s done a grade two medial (ligament) which is disappointing,” said Sanderock.
“He’s been on fire lately and really shown improvement in his game.
“It’s a big loss losing Greg. I’d probably go as far as saying we might have won that game against Hull if he’d stayed on the park.
“When he went off we had to change a lot of positions and it affected us.”
With seven first-team regulars now missing, Sandercock has drafted in more youngsters with James Green and Aaron Ollett both hoping to get a chance to impress at Headingley.