Walker's five for 18 from 14.5 overs of demanding left-arm medium-fast bowling reduced first-round winner Old Boys to all out for 90 against the defending champion on Saturday. That carried Riccarton to a healthy first innings lead of 61 in the context of a low-scoring second round.
Walker, 22, son of former Kiwi and Canterbury rugby league player Rod, removed two in the top order before snaring the last three wickets, including three leg-before-wicket decisions.
Walker has already had a Canterbury trial this season and his name can be added to the list of promising pace bowlers in the province.
It proved Riccarton, even without key pace bowlers, Neil Maxwell (gone to Australia) and the injured Wayne Stead, will not relinquish its title easily. Walker, 22, was well supported by teenager Hayden Shaw, a Shirley Boys' High School student, who bowls at a lively clip.
After a steady start few of the Old Boys batsmen could make much progress and the return of former New Zealand player Llorne Howell, playing his first game since a shoulder operation in the off season, was low key.
Earlier Riccarton, after being sent in, had grafted its way to 151 against one of the better bowling attacks in the nine-team competition. Openers Danny Grafton and Glenn Foulkes added 54 for the first wicket to steer Riccarton through the dangerous opening period while wicketkeeper-batsman Blair Miller gave the innings some substance lower down with an unbeaten 35 from 52 balls including five fours.
Leg-spinner Regan Mitchell fared best of the Old Boys bowlers from a long spell.
Old Collegians are poised for first innings points and a useful first innings advantage against Sydenham after a lower-order revival helped the visiting side through to 200 at Sydenham Park.
The Old Collegians innings was well placed at 88 for one after a 75-run stand between Scott Taylor and batting mainstay Mark Rountree but it then subsided to be 110 for seven.
Dave Cartwright, ably aided by teenager Greg Crean, led a resurgence with the last three wickets adding 90 runs. Sydenham slow bowlers Hamish Barton and Kieran White had plenty of work with Old Collegians batting 74 overs.
Sydenham's reply was disappointing with only Colin Wood getting under way against an Old Collegians attack led by Simon Harding, Andrew Kininmonth, and Andrew Hughes.
At stumps Sydenham still needed seven runs to avoid the follow-on.
On the slow pitch and long grassy outfield scoring was slow at Burnside Park and in Burnside West-University's first innings of 146 from 69 overs only four boundaries were struck.
East struck early after Burnside chose to bat first with two wickets falling for seven but Gerald Barrett and Mark Hastings scored 84 in 103 minutes for the third wicket. Hastings struck two sixes and two fours in his innings of 48 while Barrett hit one six and two fours.
Slow left-armer Carl Anderson and medium-pacer David Grocott were the most effective bowlers who all struggled on the unresponsive pitch.
East in turn began badly, losing the openers for two runs against the lively Burnside attack led by English medium-fast professional Aaron Laraman. He bowled at brisk pace with sharp lift.
While those three games had delayed starts no play was possible in Lancaster Park-Woolston's game against Marist at Garrick Park.
Friday night's storm blew the covers off the pitch and it was saturated. Although pitch conditions improved later in the day it was decided to play the match as a one innings affair on Saturday with 12 points at stake.
Scores
Old Collegians 200 (Mark Rountree 55) v Sydenham 94-8,
Riccarton 151 v HSOB 90 (Darren Walker 5-18),
Burnside West-University 146 v East-Christchurch Shirley 37-3,
Lancaster Park-Woolston v Marist, no play.