And the Blues manager has singled out the midfielder as one of the big assets to emerge amid his side’s string of midfield injuries.
Tunnicliffe’s run at Fratton Park appeared to be over last summer, with the 29-year-old firmly underdogs as he entered his second season following his arrival from Luton.
A move to AFC Wimbledon was mooted, as well as interest from MLS and the Australian A-League, with no change materializing.
After coming on as an 89th minute substitute in the 2–2 opening day draw at Sheffield Wednesday, Tunnicliffe did not feature until the 3–2 defeat at Ipswich on 1 October.
That was the catalyst for 10 appearances as injuries hit hard in the middle of the park though, with the likes of Louis Thompson, Marlon Pack and Tom Lowery sidelined.
Eight of those involved in the turnaround came as starts, before Tunnicliffe returned to the bench against MK Dons last weekend.
Jay Mingi has been another to take advantage of the opportunity and has seen his value rise through midfield absences.
Cowley highlighted the former Manchester United pupil’s conduct as key to enabling his revival at Pompey.
He said: “Tunni has played well.
“He has been very professional and works well every day.
“Like Kieron (Freeman), he’s popular within the group.
“As a manager you can only pick 11 or 18 (in the squad) though.
“It’s been good and it’s been one of the positives from the injuries we’ve had.
“The positive has been that an opportunity has been created for someone else.
“This has been the case with both Jay Mingi and Ryan.
“Both have taken advantage of their opportunities.”