After the win, Anderson improved his head-to-head record against Nishikori to 4-3, earning his second victory in a row this year against the Japanese player, following his NY semifinal triumph.
With a victory on Sunday, Anderson will qualify for the ATP Finals.
Against Verdasco, Anderson hit nine of his 19 aces in the opening set.
"We were playing for 30 minutes and there had only been four games". He used his first break point to close out the first set before running into a 3-0 lead in the second.
Anderson, after multiple errors on his backhand side when serving for the set, kept faith in the groundstroke and soon converted his third set point with another driven backhand to force an error from his opponent.
The ATP World Tour 500 trophy marks the biggest title run of Anderson's career.
Now in ninth place, Nishikori with a win could move to within 125 points of the cut for the eight-man event in London next month.
But first he must overcome Anderson, the 32-year-old Wimbledon finalist who took nearly two-and-a-half hours to battle past Verdasco.
A victor of 11 events, Nishikori hasn't triumphed since winning in Memphis in February 2016.
Second seed Anderson won 91 per cent of points behind his powerful first serve, Nishikori unable to fashion a break as his wait for a first title since February 2016 goes on.
He has lost eight straight finals since. The Japanese, ranked 16th in the ATP Return Leaderboard that measured player's performances during the last 52 weeks, earned his first service break at 5-4 and sealed the set with an aggressive forehand victor.
Soon, he completed his 250th hardcourt tour-level career victory with a pinpoint backhand victor up the line.