The second seed was out on the All England Club's Aorangi Park practice courts at midday on Thursday for an hour-long session with hitting partner Dani Vallverdu.
Vallverdu served at Murray from well inside the baseline to try to mimic the delivery of 6ft 8in Janowicz, who has served 31 aces more than anyone else in the tournament.
The Scot needed almost three and a half hours to get past Verdasco, recovering from two sets to love down for the seventh time in his Grand Alam career.
It was a tense evening on Centre Court that no doubt took a lot out of Murray, but he expects to have fully recovered in time to face Janowicz.
He said: "I'm feeling pretty good considering, I felt good today [Thursday] (in practice). I slept for about eight and a half hours so that was pretty good.
"Normally (a match like that) does take an emotional toll but I should be recovered by tomorrow [Friday]."
Murray had not dropped a set prior to Wednesday's match and was roared home by the Centre Court crowd.
The high of winning such a contest could prove a boost to Murray in his title bid but world number one Novak Djokovic, who is seen as the Scot's main rival for the trophy, has looked mightily impressive in reaching the semi-finals without dropping a set.
Murray said: "The next match will be different. I'm sure Novak is pretty happy with where his game is at just now.
"I'm happy to be in the semis. Regardless of whether it's been five sets, or the first matches were in three sets, it makes no difference."
Murray has never been one to hide his emotions and at the end of the second set on Wednesday the BBC was forced to apologise after broadcasting the 26-year-old's expletive-laden rant at himself.
Using up emotional energy in that way was seen as one of Murray's big weaknesses but he has certainly become calmer on court since beginning work with coach Ivan Lendl.
Murray said: "I think I'm much better at (getting the balance right) now than I was in the past. It's something you learn with playing matches and with age, being more mature. That's it.
"Obviously a lot of players get frustrated on the court but you need to try and find a way to respond and not get too down on yourself. Providing it's for a point or two points (it's okay). But it shouldn't be affecting me for three, four games at a time.
"It may have done in the past but I don't think that's the case anymore."
Janowicz is a surprise semi-finalist in some ways being only the 24th seed and a relative newcomer to the ATP Tour.
Last year the Pole had to qualify for Wimbledon, going on to reach the third round, and he has enjoyed a rapid rise since then.
The biggest breakthrough for the 22-year-old was his run to the final of the Paris Masters last November, which included a third-round victory over Murray.
That lifted Janowicz into the top 30 and he has not looked back since.
He has benefited from the fall of seeds around him but was very impressive in beating compatriot Lukasz Kubot yesterday, firing down 30 aces in three sets.
Murray said: "It will be a very tough match. He has a big serve. He's a big guy with a lot of power. He also has pretty good touch. He likes to hit drop shots. He doesn't just whack every single shot as hard as he can.
"He's played extremely well here, I think. He had a tough match in the (fourth) round against (Jurgen) Melzer but apart from that he's been pretty convincing."
Murray first played against an 18-year-old Janowicz in Davis Cup in 2009, and is not surprised to see the Pole come through.
He said: "Players have certainly been aware of him. There are several other talented guys all around the same age like (Grigor) Dimitrov.
"I'll need to be on my game from the outset, and there might not be that many chances during the match, so I'll have to take them when they come along.
"I'll need to return well for the whole match but it's a strong part of my game and a challenge I'm looking forward to."
Murray, meanwhile, has called on the Centre Court crowd to get behind him from the start and not wait until he is in trouble to raise the roof.
He said: "When I went behind, the crowd definitely got right behind me and made a huge, huge difference.
"If they can be like that from the first point to the last in all of the matches, it makes a huge difference."