Starting from fifth on the grid, Walker shot to second by the first corner in both races. In the opener he held third right until the final two laps and eventually ended fifth. In the second pace-car interrupted race he was second for the first eight laps before dropping back, finishing eighth. In both cases from the mid-point onwards, he suffered from a lack of rear grip.
Rizla Suzuki's Cal Crutchlow also struggled for grip during both races despite showing early on he could run with the top riders. He finished bravely with 13th and 18th places on his debut in the British Superbike Championship.
Ducati's Gregorio Lavilla won both races, held in glorious warm sunshine.
The second round of the Bennetts British Superbike Championship is at Rizla Suzuki's home circuit of Thruxton in Hampshire next weekend, with race day on Sunday, April 9th.
"It's been a frustrating day as we certainly had the pace to run at the front and compete for the podium. At the half-way point of both races my bike lost rear grip - it was like a switch was flicked and there was nothing I could do about it. Tyre choice wasn't easy this weekend so we'll be working hard with Dunlop to ensure we get it right at the next round.
"Two top-10 finishes give me a solid start to the season and I am absolutely delighted to be back riding in front of the British crowd again; it's the best ever motivation. Thanks to all the 'Stalker' fans and I hope you enjoyed the racing!"
"I didn't get quite the same storming starts as Chris in either race but I had a lot of confidence in my Rizla Suzuki and was carving my way towards the front when I started to lose rear grip. In both races I was wheel-spinning everywhere and that is not the way to make a fast lap.
"It's certainly not the start to my Superbike career that I wanted but I'm taking the positives from here. My Rizla Suzuki is fast, handling well and able to compete towards the front of the field. Once I get the tyres to last race distance, it's going to be a very different story. Roll on the next round."
Simon Buckmaster - Team Manager:
"Chris and Cal had the pace to race for the podium but ended up down the results sheets because of a lack of rear grip. They tried different tyres for the two races and while improvements were found, they didn't work as planned. We'll be working with Dunlop to find tyres better-suited to our powerful and fast Rizla Suzuki GSX-R1000.
"Well done to Chris for showing tremendous courage, determination and skill. He had us all on the edge of our seats fighting at the front and it's fantastic to witness the support he has in the crowd - it really keeps him motivated like nothing else can.
"My hat goes off to Cal; making your Superbike debut is not easy and he gritted his teeth and brought the bike home in difficult circumstances. He also proved his undoubted skill and ability and will have much better days.
"It's a quick turnaround for Thruxton next weekend and we are looking forward to putting on a good show for our home crowd. See you there."
Race One Results: 1: Gregorio Lavilla (Ducati) 28:56.903, 2: Leon Camier (Honda) +1.701, 3: Jonathan Rea (Honda) +4.576, 4: Shane Byrne (Honda) +5.699, 5: Chris Walker (Rizla Suzuki) +6.357, 6: Leon Haslam (Ducati) +14.868, 7: Tom Sykes (Honda) +20.794, 8: Ryuichi Kiyonari (Honda) +21.760, 9: Tommy Hill (Yamaha) +26.591, 10: Michael Rutter (Kawasaki) +30.829. 13: Cal Crutchlow (Rizla Suzuki) +38.212.
Race Two Results: 1: Lavilla 31:09.132, 2: Rea +1.308, 3: Camier +2.103, 4: Haslam +3.834, 5: Sykes +10.456, 6: Karl Harris (Honda) +10.465, 7: Rutter +11.154, 8: Chris Walker (Rizla Suzuki) +11.261, 9: Simon Andrews (Yamaha) +11.676, 10: Dean Thomas (Suzuki) +12.317. 18: Cal Crutchlow (Rizla Suzuki) +21.563.
Championship Positions (after one of 13 rounds) 1: Lavilla 50, 2: Camier 36, 3: Rea 36, 4: Haslam 23, 5: Sykes 20, 6: Chris Walker (Rizla Suzuki) 19, 7: Byrne 16, 8: Rutter 15, 9: Kiyonari 13, 10: Andrews 12. 16: Cal Crutchlow (Rizla Suzuki) 3.