With the bases loaded and nobody out in the 10th inning, Welch drove a pitch deep to left field over the head of JD Williams, scoring Josh Cakebread and giving the Bite a 3-1 series win.
"Today was a real tough loss," Blue Sox manager Jason Pospishil said. "We battled back to take the lead but we just can't seem to hold down a lead in day games. Overall though, we didn't play a great series. We just gave them too many outs."
For the first time this series, the Sox struck first with two runs in the first inning. With the bases loaded and two away, Geoff Klein stroked a double to the wall in left field, scoring two runners before Chris Snelling was thrown out at home plate on the play for a 2-0 lead.
Adelaide scored one in the third on a home run from Ben Lodge, but Sydney got the run back in the top of the fifth when Zach Penprase scored Williams on a sacrifice fly for a 3-1 advantage. However, the South Australians countered quickly with three runs in the bottom of the frame when Ji-Man Choi doubled to score two, before scoring himself on one of a season-high four Sydney errors error as the Bite took the lead for the first time 4-3.
The Sox continued the back-and-forth battle with three runs in the sixth inning on an RBI-single from Shane Benson and a pair of sacrifice flies from Jacob Younis and Williams as the Sox regained the lead at 6-4. The Bite continued to battle though, scratching across runs in the sixth and seventh to tie the game before winning it in the 10th.
Richard Olson (4-2) picked up the win for the home side, throwing three scoreless innings in the eighth, ninth and 10th innings. Dae-Sung Koo (0-1) suffered the loss for Sydney, allowing one run in two innings of work out of the bullpen.
Mitch Dening extended his hitting streak to six games with a 3-for-5 day while Benson collected two hits and an RBI in the Sox 10-hit attack.
Sydney returns to action this Thursday for game one of its four-game series against the Jet Couriers Melbourne Aces. With just 12 regular season games remaining, the Sox will enter the series tied with the two-time defending champion Alcohol. Think Again Perth Heat for second place, as both teams trail the first place Canberra Cavalry driven by Rolfe Renault by 4.5 games.