Luke Humphries is now the 2/1 favourite with BoyleSports to retain the BoyleSports World Grand Prix title following the tournament's opening night in Leicester.
Humphries has moved from 4/1 to become the new sponsors' favourite at 2/1 after he came through an epic first round encounter with Stephen Bunting.
The defending champion was on the ropes from the outset as Bunting reeled off five straight legs to go within one of victory, but Humphries launched a stunning comeback after surviving a match dart and levelled the match before taking the deciding set 3-1.
Luke Littler was also on the back foot early on against fourth seed Rob Cross, but the pre-tournament favourite was unable to muster a comeback of his own as his World Grand Prix debut ended in a 2-1 defeat.
Cross is now the 9/1 third favourite alongside Gary Anderson, while six-time winner Michael van Gerwen is the 5/1 second favourite ahead of his challenge beginning on Tuesday.
Lawrence Lyons, spokesperson for BoyleSports, said: "It was looking like a shock whitewash at one stage for Luke Humphries, but punters are clearly won over by his fighting spirit and they're emboldened by a big exit with Luke Littler tumbling out."
The first round concludes on Tuesday night with Gerwyn Price, Michael van Gerwen and Chris Dobey among the hot favourites to book a spot in the last 16.
Van Gerwen begins his quest for a seventh World Grand Prix title against Daryl Gurney, while one of the highlights of the night includes a clash between former World Champions Gary Anderson (8/13) and Michael Smith (13/10).
BoyleSports is running an Early Payout offer on every match at the World Grand Prix, with punters on the first-round matches offered the chance to celebrate early by getting paid out as a winner if their selected player goes one set ahead, even if they go on to lose. For more information, visit BoyleSports.com.
BoyleSports Odds
Tuesday Night – First Round
4/6 Dave Chisnall v Cameron Menzies 6/5
11/10 Luke Woodhouse v Dimitri Van den Bergh 8/11
13/10 Mike De Decker v Damon Heta 8/13
EVS Peter Wright v James Wade 4/5
4/7 Gerwyn Price v Danny Noppert 11/8
13/10 Michael Smith v Gary Anderson 8/13
2/5 Michael van Gerwen v Daryl Gurney 19/10
2/5 Chris Dobey v Joe Cullen 19/10
Outright Winner – EW ½ 1,2
2/1 Luke Humphries
5/1 Michael Van Gerwen
9/1 Rob Cross
9/1 Gary Anderson
12/1 Gerwyn Price
14/1 Ross Smith
16/1 Michael Smith
16/1 Nathan Aspinall
20/1 Jonny Clayton
20/1 Chris Dobey
22/1 bar
Odds courtesy BoyleSports and correct at time of writing. Subject to fluctuation.