Exeter scored both of their tries in the final 20 minutes as they stormed home to victory over London Irish at the Madejski Stadium.
The visitors rattled on 15 unanswered points in the final quarter, including tries to Dean Mumm and Ben White, to secure a 29-23 success.
For the opening hour Irish were the better side, showing greater enterprise than a lethargic Exeter and with visitors' wing Tom James in the sin bin, the hosts appeared sure-fire winners.
Irish had already gone over through Nick Rouse and Marland Yarde in each half but they came to a standstill as 19 points from the boot of Gareth Steenson ensured Exeter sailed home.
Irish, crippled by a huge injury list with 12 of their 35-man squad unfit, suffered two further injury blows during the course of the match and ultimately that factor told against them.
Both teams were forced to make changes from last week's winning sides.
White came in for hamstring victim, Dave Ewers, in the back row for the Chiefs while Irish lost Jon Fisher, Chris Hala'ufia and Guy Armitage to be replaced by Declan Danaher, Bryn Evans and Fergus Mulchrone in their original line-up.
In addition Topsy Ojo picked up a hamstring injury in the warm-up resulting in Alex Lewington having a late call up.
Exeter took an early lead with a penalty from Steenson after Yarde was penalised for crossing before Irish had their first chance for points but Ian Humphreys fired wide from close to the touchline.
Steenson missed a penalty attempt but it was Irish who had the better of the opening quarter as they attempted to move the ball at every opportunity. The visitors' defence was stretched but they kept their line intact so it was left to Humphreys to tie up the scores with a successful penalty.
When Exeter were awarded another penalty, which Steenson kicked, referee Andrew Small spoke to both captains as the game was being riddled with ill-discipline.
The players did not seem to heed Small's warning as Irish were again penalised allowing Steenson to kick his third goal.
After 28 minutes came the first real prospect of a try. Following a close-range lineout, Halani Aulika appeared to drive over but the TMO ruled that excellent defensive work from Steenson and James Scaysbrook had held up the prop.
However Irish were not to be denied for long as from the next scrum Rouse crashed over for a try which Humphreys converted to give Irish the lead for the first time.
That lead should have been extended but Humphreys missed with a penalty after Tom Johnson was penalised for a dangerous challenge with the Exeter number eight fortunate to escape without a yellow card.
Just before half-time, the beleaguered Irish suffered another hammer blow when their best player, Aulika was helped from the field with a leg injury.
Steenson put the Chiefs back in front with another penalty before Lewington made a neat break. The young full-back avoided Johnson's tackle putting Exeter under pressure which forced James to commit a cynical foul by pulling back a support player. James was yellow carded and Humphreys kicked the penalty.
The game then appeared to change dramatically in Irish's favour when immediately from the re-start, Bryn Evans, tore away on a 45 metre run to put the Chiefs on the back foot. The ball was recycled for Lewington to send Yarde in for the try which Humphreys converted, before kicking a penalty for a 23-12 lead.
Back came Exeter, Jason Shoemark, appeared to have scored but his effort was harshly ruled out by the TMO but Exeter got their reward when Steenson kicked his fifth penalty.
John Yapp was yellow carded for dragging down a maul with Chiefs taking full advantage by immediately scoring their first try through Mumm with Steenson converting to reduce the arrears to one point.
Jebb Sinclair was another injury casualty for Irish before Exeter completed their astonishing comeback with a try by White converted by Steenson.