Both shot-stoppers have been on trial this summer. Preston has played two 45 minutes for the Bucks and Wycherley played the second half of Tuesday’s 1-0 defeat at Barwell.
Cowan wants another goalkeeper to add to his Telford squad to compete with Sheridan Martinez for the No.1 spot.
“Callum has played two 45s now so I’ll be having talks with him in the next couple of days,” said Cowan.
“Andy will not be happy with the goal but he’s a very good very technical goalkeeper. We’ll be having a chat.”
Preston, from Stafford but a former cricketer in Welshpool where he grew up, is formerly of Birmingham’s youth team and briefly played in League One with Crawley.
Cowan added: “It will only be one keeper. Cal and Andy are trying to make an impression but we’re open.”
Wycherley, from Telford, left The New Saints this summer. The highly-rated 20-year-old is keen to play first-team football.
But he was unable to see out a clean sheet on his Bucks bow as Cowan’s men conceded a goal shortly after half-time on a tough playing surface in Leicestershire. A loose clearance was charged down and put into the net by Owen Story for the hosts.
While frustrated not to win the game against lower-ranked Barwell, but stressed extenuating circumstances played their part in the Bucks second straight defeat.
He added: “It was not the result we wanted but I was really happy with the first half performance.
“It was difficult for the players with a bobbly pitch, which was not ideal.
“It was good to get the players together and improve on things from the Villa game and again we came through with no injuries.
“We gave an opportunity to a few trialists. There were numerous opportunities to score, we were just missing a goal.”
Full-back Tyler Little, who has been an ever-present throughout the summer for Cowan’s men, again featured.
There also a place in the starting XI for former skipper Jack Rea and striker Matthew Barnes-Homer as the Bucks boss continues to help them with fitness.
The boss continued: “They’ve been coming and getting game time and will be happy with 60 minutes and if somebody came to watch them they’d be very impressed, I’m sure.”