Joe Panik's 2015 season ended on Sept. 9 because of an ailing back.
"Well, Mike (Krukow) and I knew he had a fracture. But that's not for us to throw out there," Kuiper revealed on KNBR 680 on Tuesday morning. "So we knew that when he came back that second time, and he told everybody he was feeling pretty good, we knew he was lying.
"And I told you before, he's a great liar. Most guys are when they get back on the field."
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SIGN UP HERE Over 97 games from April 6 to Aug. 1, Panik hit .309 with seven home runs and 37 RBI, and was named to his first All-Star team.
The Giants then shut the second baseman down from Aug. 2 to Sept. 6.
In his first start back on Sept. 8, Panik went 2-for-3 with a home run and a double.
"Feeling good," Panik told Kuiper and Krukow after the Giants' 6-2 win in Arizona. "Couple hits and a home run kind of helps. But we'll see tomorrow. You're gonna have some good days and some bad days. But first couple days I've been feeling pretty good."
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Apparently, he wasn't actually feeling pretty good because he was pulled late in the next day's game, and didn't play again the rest of the year.
Despite the frustration over his season being cut short, Panik was optimistic his issue would not be chronic and that he would be fine in the long-term.
[RELATED: Panik among injured Giants who returns at '100 percent']
At FanFest on Feb. 12, he confidently said he feels "100 percent," and shared that he was cleared by team doctors in mid-December.
"It was right around the time of all the signings," he said, smiling. "I was able to fly under the radar. I got tested and everything had healed up. I got cleared and was able to have my full offseason workouts. I'm good to go. I'm happy to be feeling good and going back out on the field to show that I'm healthy. My swing feels strong."
Although Panik looks to be full-steam ahead, the Giants are going to play it safe with him.
"What you have to figure is, 'OK, is this gonna be something that's gonna bother him for the rest of his career?' And if you believe our training staff, and I do, and the doctors, once this fracture heals up, that's it, he's good to go," Kuiper said. "And it shouldn't be an issue again. And that's the best news because he's a really hard guy to replace.
"So good for Joe. He's healthy. I believe him now (laughing), and it's time to see him on the field. I'm happy for him."