Thomas Frank admitted he may have tinkered too much after Brentford were almost on the end of a Carabao Cup shock.
Last season's giantkillers nearly got a taste of their own medicine before coming from behind to beat Forest Green 3-1.
Brentford, who knocked out four top-flight sides on their way to the semi-finals last year, fell behind to an early goal from Rovers' Jack Aitchison.
Now a Premier League club themselves, the Bees suddenly found themselves a potential scalp for League Two Rovers.
Frank made nine changes to his line-up and the lethargic hosts looked second best for long spells, in stark contrast to their buoyant display against Arsenal 10 days earlier.
The Bees boss had to call for reinforcements from the bench at half-time in the shape of Sergi Canos and Bryan Mbeumo.
And second-half goals from Yoane Wissa – his first since an £8.5million summer move from Lorient – Mbeumo and Marcus Forss averted an upset at the Community Stadium.
Frank said: "In the first half Forest Green deserved a lot of credit, I think they were the better side. They were brave, energetic and played through us.
"We had a massive chance and then made a mistake and were 1-0 down. We did not have enough quality on the ball.
"At half-time I said to calm down. In the second half we changed the system and that helped, and in the end I think we got a well deserved win.
"Of course, it's clear some of the guys have been more regular starters and have a bit more quality in these situations – so that definitely helped.
"Maybe I changed too many players, plus I changed the system. Maybe that didn't help us. I'll analyse that a little more."
Forest Green lost Ebou Adams to a straight red card for a late tackle on Vitaly Janelt.
But manager Rob Edwards, whose side have a 100 per cent record in League Two, took plenty of positives from their display.
"I'm really, really proud of the lads, they were excellent," he said. "They were brave, they showed good quality and in the first half caused them some problems.
"We probably made them angry. They made changes at half-time and their substitutes shifted the dynamic of the game, but we stayed in it for a long time. We had a right good go.
"It's strange. We've lost and we're out of the cup but if you're going to lose that's the way to do it. We competed with a team like this and it gives you a lot of pride and a lot of confidence."
