Matt Roller is an assistant editor at ESPNcricinfo. @mroller98
Somerset 337 and 196 for 9 (Abell 53, Banton 52) lead Surrey 308 (Curran 80, Foakes 63, Siddle 6-51) by 225 runs
Foakes dived to his right while taking a catch to dismiss Tom Banton off Reece Topley's bowling, while Overton dived to his left at first slip and made contact with Foakes' head with his right shoulder.
Sam Curran ran over to celebrate but immediately signalled to the dressing room as Foakes lay on his back and covered his face with his left arm. Surrey's medical staff rushed on with a stretcher during a ten-minute delay, though Foakes managed to walk off the field with help from Alex Tysoe, the lead physio.
"He's under observation with the physios," Azhar Mahmood, Surrey's assistant coach, said. "Concussion tests are going on and hopefully he'll be fine tomorrow. It was shoulder to neck. I think there was a cut. There was some blood coming out of his ear but I'm not sure if it was internal or outside."
Ollie Pope took the gloves for the final hour of the third day. Jamie Smith, who was left out of this game, could come into the side on Sunday as a concussion replacement depending on the outcome of Foakes' tests.
This was the second time in a year that Foakes has suffered a freak injury at The Oval, after he tore a hamstring while slipping in his socks on the dressing-room floor following a Championship game against Middlesex last May.
With Jonny Bairstow and Jos Buttler rested after their involvement in the IPL, Foakes had been in line to make a home Test debut against New Zealand. Instead, he was ruled out for four months, only returning to Surrey's first XI for their final Championship match of the season, a high-scoring draw against Glamorgan.
The timing of his latest injury will be a concern to England, with the first Test of their summer - again against New Zealand - just under six weeks away. Foakes has started the season with 240 runs for twice out across three appearances and is the incumbent wicketkeeper after taking the gloves in the Caribbean.
Foakes' injury appeared to disrupt Surrey's rhythm as they looked to restrict Somerset in their second innings. Topley had taken three wickets in seven balls - including that of Banton, their last recognised batter - before the stoppage in play but Surrey went 11.5 overs without one under the floodlights.
But Jack Leach chopped on off Overton before Jordan Clark struck with the final ball of the day, leaving the game in the balance heading into Sunday. Surrey were two bowlers down with Curran limited to 15 overs in the match by the ECB as he returns to fitness and James Taylor suffering from back spasms, but Overton and Topley sparked a collapse of six wickets for 64 runs late in the day.
Somerset's lead was 225 heading into the final day thanks largely to an 89-run partnership for the third wicket between Banton and Tom Abell, both of whom made fifties. Abell had managed 109 runs in his last 14 first-class innings heading into this game but made 203 for once out in the match, scoring freely and hitting boundaries on both sides of the wicket before edging behind off Ryan Patel's medium pace.
For Banton, this was a significant innings, only his second of the summer after missing the first two rounds of games due to a fractured finger. He started last year opening the batting, then became a specialist No. 7 and finished the season out of the side after averaging 18.84, but vowed in pre-season that he would "come back as a new player this year" following technical tweaks over the winter.
He was occasionally troubled by Overton, edging his first ball wide of the slip cordon for four, but dug in for just over two hours and played confidently through the covers and off his pads. It was notable that he came in at No. 4, ahead of James Hildreth, having enjoyed most of his red-ball success in the middle order in his breakthrough season in 2019.
Surrey had been bowled out for 308 soon after lunch, with Peter Siddle taking four of the last five wickets to finish with 6 for 51 from his 26 overs in his 200th first-class game.
In his first appearance for seven months after a stress fracture of the lower back, Curran had threatened to make the first hundred of his professional career, scoring fluently and lofting Leach for a straight six, but ultimately fell 20 runs short.
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