WIMBLEDON, England—Andy Murray has been pushing the All England Club crowd to get behind him in a more vocal way this year; to show him, as they say, some love. And when you sit among the fans here, you can see why he’s asking. The tennis lovers of Great Britain want Murray to win, no question about it. Unfortunately, they want him to win in the worst way—literally. If you’d like to know what a climate of fear feels like, try to find your way to Centre Court during one his matches. The most common phrases I heard in the stands today weren’t “Let’s go!” or “Come on!” or “That’s it!” They were, “Oh, God,” “Oh, Jesus...no,” and “That was a stupid challenge, Andy.” After one routine Murray miss, someone a few rows back told his friend knowingly, “You never see Novak Djokovic do that.”

This was the scene of misery that Jerzy Janowicz happened upon today. It’s hard to think of a more terrifying figure to an already jumpy Centre Court spectator. With his towering 6’8” frame, his 140-M.P.H. serves fired like a machine, his raspy bellow, his provocative, loose-cannon personality, and his constantly clapping supporters, Janowicz could have been cast as a tennis version of a villain in a Hollywood Cold War movie—the "Polish Rifle" would be the marquee nickname, of course. Early in the match, whenever Janowicz launched a serve, the woman next to me covered her eyes with her hands. I can’t say I blamed her. Jerzy serves 140, but it sounds closer to 180.

Plus, as it quickly became clear to everyone, he can play. “Butterflies” is not a word I would associate with Jerzy Janowicz, and for a first-time Grand Slam semifinalist he didn’t appear especially nervous. In fact, after he saved a set point at 4-5 in the first with a 121-M.P.H. second serve, he started to look more comfortable than the home favorite. From there to the end of the set, Janowicz dominated. If he wasn’t hammering his forehand, he was floating in deceptive drop shots. When Murray double-faulted to lose the tiebreaker, the fans’ fears were confirmed. A security guard near me seemed to speak for everyone inside Centre Court when he asked, with a sigh, “He’s not gonna stuff it now, is he?”

As if on cue, though, the villain in the piece revealed a flaw. If you live by the 120-M.P.H. second serve, at some point you’re likely to die by it, too. Janowicz’s demise began in the first game of the second set, when he threw in two double faults and was broken. Some of the fear in the stadium lifted, and Murray served out the set from there. Janowicz would finish with 11 double faults.

But a straightforward Murray romp from that point on would have been too easy, for both player and crowd. Instead, he was broken at 1-2 in the third set on a nervous, bizarrely weak slice backhand that Janowicz carved for a drop shot winner. Murray was tight again. This time, though, nerves may have worked in his favor. With Janowicz serving at 4-2, 30-30, Murray hit a tentative forehand that looked like it was destined for the net. Somehow, it crawled to the tape, clipped it, and bounced over for a winner. On the next point, Janowicz revealed a second flaw: His tendency to fall in love with the drop shot. Murray was there to track this one down and bury a forehand for the break.

“Everything basically collapsed,” Janowicz said later in his high-pitched voice, as he played with his fingernails at the interview table, “after this one point when it was 30-all, third set, 4-1 [the score was actually 4-2] for me. He did the tape, the ball just roll over.”

That “roll over” did indeed spell the beginning of the end for Janowicz. Murray went back on the attack and swept the last five games of the set. He was more confident with his forehand, and his serve began to catch fire. He hit three aces to hold for 4-4, hit another at set point, and used his first serve to drive him through the fourth set, after the roof had been closed. Murray finished with 20 aces, though he was helped by some poor returning by Janowicz. In the end, the wily, defensive-minded veteran had exposed enough of this talented young player’s weak spots to come away with a 6-7 (2), 6-4, 6-4, 6-3 win.

“I’m a little bit disappointed,” Janowicz said. “Today I didn’t play my best tennis. I think it was the second-worst match during this tournament [for me]. I was struggling a little bit with my serve.”

Despite that, Janowicz showed off the visceral, galvanizing quality of his power game today. Along with Juan Martin del Potro, who took Novak Djokovic to five sets earlier, Jerzy sent a warning to the two top seeds, each of whom is a defender first, that attack-minded tennis could be on the rise again very soon. If there was any question before this tournament who was more likely to succeed in the immediate future at Wimbledon, Janowicz or his fellow rocket-launcher, Milos Raonic, the fortnight dispelled it. Janowicz, no longer the villain in the piece, gave the crowd a thumb’s up as he walked off to a standing ovation. Asked what he told Murray as they shook hands, Janowicz looked up from his fingernails and said, “I don’t feel like losing [to the] runner-up, so I wish him good luck.”

"Deep down I'm really happy," said Janowicz, who is also a personality to watch. Despite his famous volatility, he seems able to keep his losses in perspective. "This was my first Grand Slam semifinal, so tomorrow I'm going to be OK."

The hero, fears to the contrary, moves on to his second straight Wimbledon final. Murray said that last year he felt relieved when he won his semifinal; this time he felt “happier."

Murray should feel happy about this one. He found a way to come back from a slow start and break down a dangerous player; he forced himself to be more aggressive and dug his way out of a big hole at a crucial moment; and he finished with 49 winners against just 15 errors. What Murray will most want to match in the final is the quality of his serving. Asked how he’ll defend his second serve against Djokovic’s excellent return, Murray said, “You don’t have to hit as many second serves if I serve like did this evening. I served well tonight, and that helps.”

Finally, Murray was asked about what his expectations might be for the final this year, compared to last year.

“I think I’ll probably be in a better place mentally,” Murray said. “I would hope so just because I’ve been there before.”

That was a nice, positive start to the answer, eh? Soon, though, a few doubts began to creep in.

“I would hope I would be a little bit calmer going into Sunday,” Murray continued. “But you don’t know. You don’t decide that.”

A few minutes later, it was all over, Murray couldn’t keep the cheery charade going any longer:

“I might wake up Sunday,” he concluded, “and be unbelievably nervous, more nervous that I ever have been before.”

Like player, like fan, right? Show this man some love in the final, tennis fans of Great Britain.