East Shirley were the beneficiaries of a tough day for the leaders in the premier two-day competition, after they dominated the first day of their match against Sydenham at Burwood Park on Saturday.
Easts, who started the round in third spot behind ladder leaders Lancaster Park-Woolston and Old Boys Collegians, started strongly, reducing Sydenham to 74-7 before a fine rearguard by Grant Fortune (47) helped the struggling side to a competitive 153.
Six players passed 20 in Easts' reply of 246-9, with D J Lyons (47), Hamish Teale (44) and Tim Johnston (44) the best performers.
Black Cap Rob Nicol had an uninspiring return for Sydenham as he posted scores of four and two in his two innings as Sydenham were in trouble at 79-3 at stumps.
Jared Roberts picked up five wickets for Easts in Sydenham's first innings as they strive for an outright victory to continue their assault on the leaders next week.
Lancaster Park-Woolston's spot on top of the ladder is in jeopardy as they crashed from 85-2 to be bowled out for 128 against St Albans at Garrick Park.
Keryn Ambler and Michael Davidson put on 82 for the third wicket but once Davidson retired hurt for 37 and Ambler was dismissed for 45 by Matt Holstein (3-23) the rot set as Saints built a 68-run lead on the back of Greg Dawson's 73 in their total of 196-7.
Dean van Deventer and Sam van Daesdonk (both 2-45) did their best to keep LPW in the game.
English professional Ian Cockbain struck his second century of the season as Marist Harewood put Old Boys Collegians on the back foot at Redwood Park.
Cockbain struck an unbeaten 123 while Cole McConchie (39), Ken Henry (27) and Peter Younghusband (21 not out) provided cameos as Marist reached an imposing 243-4 off their 60 overs.
For OBC, Ben Bellamy (47) and Adam Hastilow (30) provided much needed fight in their total of 160-9 while McConchie (2-31) and Younghusband (2-35) showed their all-round talents.
OBC trail by 83 runs and need a strong bowling performance early on day two to keep their spot in the top two.
Burnside West University had a 122-run lead after the first day of their game against Riccarton at Burnside Park.
Mitch Croft top scored with 51 in their innings of 246 while Ben Rapson provided Riccarton's only highlight of the day as he was a lone ranger with the ball to pick up 6-78.
Riccarton scraped their way to 124-8 in reply as Dave Sewell (5-30) was the chief destroyer for BWU.
Should Todd Blackadder stay on as Crusaders coach?Related story: Coach Todd Blackadder's job at Crusaders safe