They were as difficult as always.
Isner had seven aces and won the battle of big serves with a 6-3, 7-5 victory in the final of the U.S. Men's Clay Court Championship.
"His serve was like normal and his serve today was tough for me," Almagro said. "I want to congratulate him because he's really good player and a good person and he did a good job this week and he won the tournament."
Isner won his first tournament of the year and the sixth of his career. He had a record 64 aces for the tournament. He broke the record of 60 set by Pete Sampras in 2002. Almagro leads the ATP Tour with 266 aces. He had five against Isner.
Isner had aces of 144 and 142 mph in the 10th game to hold serve in the second set.
"I've always known I could play well on clay," Isner said. "This week is surprising because the first ball I hit on clay since September was Monday when I arrived here from Idaho."
Isner also likes the River Oaks Country Club clay. He was runner-up last year.
"It suits me well," Isner said. "The court is pretty slow which I like and the balls also pretty light. That's normally a good recipe for me."
The players were on serve in the second set until Almagro was broken in the 11th game at the fourth break point on Isner's forehand that landed in front of Almagro and out of his reach. Almagro double-faulted twice in the game.
Isner then served for the match in the 12th game. He added his final ace, bringing it to match point. Almagro popped up Isner's serve to end the match.
Isner won $82,300 and Almagro earned $43,310.
Isner is second on the ATP Tour with 258 aces and he won 75 percent of his first serves against Almagro, who won 55 percent of his first serves and double-faulted four times.
Almagro lost on his favorite surface. All 12 of his tour victories are on clay. He's got a long flight to Monte Carlo to think about it.
"Right now it's difficult to say something," Almagro said. "I need to wait a while and we'll see during the flight because I have a long time to think about the match. Right now I'm not happy about the match because I lost."
Almagro broke Isner in the third game of the match at the third break point on Isner's double fault. After that, Isner faced only one more break point in the match.
Isner broke Almagro in the eighth game of the first set for a 5-3 lead. He hit a drop shot winner and slammed a forehand down the line at break point.
Almagro played in his 19th career final. He has won 12 titles, all on clay. He dropped to a 17-7 match record on the year and has two semifinal appearances at Buenos Aires and Acapulco.
Isner is the first American to appear in an ATP Tour final this year. Isner lost to Juan Monaco 6-2, 3-6, 6-3 in last year's final.
Isner had a tougher time getting to the final match with three tiebreaker sets and three, three-set matches in victories over Americans Ryan Harrison and Jack Sock, Lithuanian Ricardas Berankis and defending champion Juan Monaco of Argentina.
"I knew it would be a tough adjustment, but I knew I just had to find a way to get through my first match," Isner said. "I did and I got to my second match, which was really close. I really started to play better each and every round."
Isner won twice last season at Winston-Salem and Newport.