Thanks to a daring attack on stage 2 that was initiated on Mt. Hamilton, 50km from the finish, the cream of the climbing talent in the race has already risen to the top of the overall standings, where Rafal Majka (Bora-Hansgrohe) leads George Bennett (LottoNL-Jumbo) by two seconds, Ian Boswell (Team Sky) by 14 seconds and Lachlan Morton (Dimension Data) by 16.
Bennett's teammate Robert Gesink, the 2012 winner in California, is fifth at 45 seconds, followed by a large group 48 seconds back that includes Brent Bookwalter (BMC Racing), Sam Oomen (Team Sunweb), Andrew Talansky (Cannondale-Drapac), Vegard Stake Laengen (UAE Team Emirates), Max Schachmann (Quick-Step Floors), Enric Mas (Quick-Step Floors) and Team Sky's Tao Geoghegan Hart.
Thursday's stage will be quickly followed on Friday by the 24km Big Bear Lake time trial, so riders who can climb but are questionable time trialists will be hoping to create a big enough buffer on Baldy to insulate their GC position from a strong time trial performance by the likes of Talansky or Bookwalter.
Stage 5 starts in the city of Ontario east of Los Angeles and immediately starts heading uphill to the first intermediate sprint at San Antonio Heights. But sprints aren't the focus of this day as the route continues skyward with the first-category climb of Glendora Road.
Chris Horner, riding for Radioshack-Nissan at the time, attacked the bunch here in 2012 after losing time earlier in the race. The winner of the 2011 Tour of California started the day 2:50 down and obviously hoped to make up a large block of time with the long-range move. It didn't work, and Horner finished the stage sixth, 38 seconds down on stage winner Gesink.
Although the teams that need to make up big chunks of time will be desperate to try some similar tactics, Morton told Cyclingnews the Baldy climb neutralises team tactics, and it comes down to who has the best legs on race day.
"You can make really big time difference in the final five miles," Morton said of the Baldy climb. "I think we're in for a really big showdown."
BMC Racing director Jackson Stewart agreed with Morton – to a point.
"It's a pretty straightforward climb, but there's a lot that could happen before the climb," Stewart told Cyclingnews. "If guys are aggressive with their multiple options it could change things and change the race. But I think there's four guys there now in contention. It would be weird if it came down to where they started playing those other options, because you'd have to have all the stars aligned a little bit."
The stars have not aligned so far for BMC, with Bookwalter losing time on the Mt. Hamilton stage, but Stewart said the team is down but not yet without hope in the GC standings.
"For us, we're kind of out of the mix," Stewart admitted. "We just have to have a good climb if it's all together there, and/or we have to be aggressive. So, yeah, I think there's a little bit of tactics, because if something went early, and the right teams were in it, it's over. But it's short, and maybe nothing can really go early.
"It's hard to say what will happen really," Jackson said, "but the strongest climber should win that stage."
If that's the case, all eyes should turn to Rafal Majka, who easily appeared to be the strongest of the four riders in the stage 2 breakaway, eventually beating Bennett in a two-up sprint to take the race lead.
Majka said earlier this week that he'll be looking to add even more time to his lead on Baldy, but, as his teammate Peter Sagan pointed out in the stage 3 press conference, Majka has recently spent some time in the wind tunnel, so his time trialing skills maybe on the uptick.
Nevertheless, the Bora-Hansgrohe rider won't be leaving anything to chance and will be the rider to watch on Baldy. He'll have plenty to worry about from Bennett and LottoNL-Jumbo, however, as the Dutch team has already proved this week it can blow a race apart, as Bennett did with his stage 2 attack.