I added this as a popup to the Pompey Comic. This happened during the Sertorian war, and boii did Pompey struggle against Sertorius. Sertorius was an excellent commander and on multiple occasions got the best of Pompey. According to Plutarch, this occasion bothered Pompey quite a bit. I can imagine it's due to the fact that Pompey was so sure of himself beforehand and confident enough to boast about the situation - you know before he realized that it was actually himself that was in a bind.
In the end, Pompey was unable to reposition for fear of being surrounded. He had to watch as the city he aimed to save was captured and burnt.
This would not be the last time that Sertorius bested Pompey. The following battle at Sucro had Pompey injured, and just barely escaping with his life. If it weren't for General Metellus coming in clutch, Pompey would have likely seen a decisive defeat.
Following that battle Sertorius, who I picture as a grumpy old badass said "if that old woman [Metellus] would not have come up, I would have given this boy a good drubbing by way of lesson, and have sent him back to Rome"
And yes, Sertorius lost an eye in combat. He also had a trained white deer that went on walks with him. I am not making this up.