Flintridge Prep improved to 6-4 despite blowing a large lead and then seeing St. Michael's rally for a 10-9 lead in the top of the sixth.
"I honestly didn't have to say too much to them after [St. Michael's] took the lead," Cook said. "[Assistant] Dave Lovejoy talked to them.
"When it's 9-0, most think it's over and it's not over. We weren't making plays defensively, and we were not throwing strikes. I'm not a yeller because I don't see the point. I made it clear about them not running and hustling on the field."
Flintridge Prep responded with a surge in its half of the sixth. Parker Williams knotted the score at 10 with an RBI single and Alex Sierra made it 11-10 with an RBI double to left. Kyle McDonald, Brenden McKiernan and Karlsen Termini each drove in a run to seal the victory.
Sierra said the Rebels needed to regroup in a hurry.
"A lot of us had let up at 9-0, and we weren't playing with the same kind of intensity that we had early in the game and in the last inning," Sierra said. "You look and see that it's 9-0 and a lot of us thought we had it and we let our guard down.
"We learned that you always have to play your hardest. Once they took the lead, we had to turn it back up. We needed to step up and we did."
St. Michael's, which dropped to 4-4 and is coached by former La Crescenta resident Ralph Martin, scored five runs in the sixth to take a 10-9 lead. A run-scoring single by John Michael Mikolaycik gave the Pioneers the lead.
Cook said Sierra stepped up to rally the Rebels.
"With Alex, I expect it from him," Cook said. "He's batting ninth in the order and he's going to get some good pitches to drive."
The Rebels scored four runs in the first to take a 4-0 lead. Royce Park, Termini and Scott Tsangeos had consecutive run-scoring hits to give Flintridge Prep a 3-0 lead.
Daniel Enzminger and Williams each drove in a run to make it 7-0 in the second inning before the Rebels received a two-run double from Termini in the third to extend the lead to 9-0.