Undera kicked just one major in the first half and Stanhope led by 23 points at the long break.
After half-time, however, winless Undera added five goals to its tally.
The Undera team led by a point at three-quarter time before the Donnell effect and an improved mid-field effort saw Stanhope kick seven goals to one in the final term.
If not for Donnell’s late inspiration, the result could have been closer, although if Tom Rennie was able to convert more of his 10 shots on goal, the eventual six-goal margin could have been doubled.
Rennie finished with only two majors, as the other seven Stanhope goals all came from individual sources.
Stanhope won the match 11.10 (76) to 6.4 (40), Undera’s second-best result of the year after losing to Dookie United in the opening round by 20 points.
After that result they have been beaten by 85 points, 40 points and 158 points.
Undera remains winless on the bottom rung of the KDL ladder, while Stanhope is now in a battle with last year’s grand finalist Nagambie to stay in the top six.
Stanhope has the much improved Tallygaroopna, which is sitting third on the ladder, then see-saws between top and bottom teams with games against Violet Town (13th, second bottom), Shepparton East (fourth), Rushworth (11th) and Nagambie (seventh).
Stanhope coach Adam Lovison said best-on-ground Jack Donnell was moved from halfback into attack in the last term “to liven us up a bit”.
“He will go where he is needed, it would be nice to have two of him,” Lovison said.
Stanhope went into the game without regulars Lukas Hanslow, Rhys Smith and Zane O’Donnell, while key mid-field recruit Layne Baker played in the reserves.
Co-captain Jonathan Pearson played on ball and high half forward, working with makeshift ruckman Daniel Maher.
Daniel Flynn started at centre-half forward, while Rennie also pinch hit in the ruck.
“Undera is not as bad as it has seemed the last few weeks. If you give them a sniff, as we did, they will hang around,” Lovison said.
“They are a very well coached side by Harty. We missed a lot of shots at goal, which made it seem a lot closer.
“Tom Rennie was off target, but the promising factor is he is grabbing it and making opportunities.”
He said the Lions had trialled a new game plan where they slowed down the play and used shorter kicks to bring the ball back inboard and gain control.
“We started really well, but missed opportunities and fell away in the second and third quarters,” Lovison said.
“To the players credit, we brought it in the last for the win.”