How did we get here?

Through their first four games this season, Stanford and Cal appeared headed in opposite directions.

Let’s hit the replay button:

Stanford beat Oregon 38-31 in overtime at Eugene, Ore., to run its record to 4-0 and climb to No. 7 in the AP Top-25 poll.

A week later, Cal played its fourth game. The Bears lost. After a bye. At home. To that same Oregon team. And it wasn’t close, 42-24, triggering a three-game slide.

On Saturday, Stanford and Cal will meet in the 121st Big Game at Berkeley. And guess what? Both teams are 6-4, each having won a week ago to become bowl eligible.

Here’s how we got here:

Stanford craters: Well, crater may be a bit strong. But it’s fair by the program’s impossible standards. After its 4-0 start, the Cardinal lost four of five games for the first time since the close of 2008, Jim Harbaugh’s second season.

Cal flips its script: The Bears seemed on their way to repeating the disappointment of 2017, when they started 3-0, then lost five of six, eventually failing in a bid to become bowl eligible. This time, after opening the Pac-12 with three losses, they responded by winning three of four.

A defense emerges: Stanford has been one of the Pac-12’s best defenses for a decade. Cal just the opposite. But while the Cardinal has allowed 38 points or more three times for the first time in seven seasons, coach Justin Wilcox’s squad has held four consecutive conference opponents under 20 points for the first time since 1958. Unimaginable just two years ago.

All you need is Love: Stanford running back Bryce Love assembled one of the greatest seasons in college football history last season. The Heisman Trophy runner-up rushed for 2,118 yards and set an NCAA record with 13 runs of 50 yards or longer. This fall, hampered by injury, he has run for just 580 yards. The consequences to the team were inevitable.

O-line expectations: Stanford was supposed to have one of its elite offensive lines. Cal, with all five starters back, also had high hopes. Even given Love’s limitations and injuries to the line, it’s hard to imagine a Stanford team ranked last in the Pac-12 in rushing. Cal has run a bit better than that, but is 11th in the conference in scoring. It all starts up front. Or doesn’t.

Stanford changes stripes: Unable to unleash its power running game, coach David Shaw saw junior quarterback K.J. Costello and a strong corps of receivers as an antidote. Costello has responded by throwing 23 touchdowns, second-most in the Pac-12.

Juggling act: The Bears began the season with Ross Bowers, a 3,000-yard passer last season, as their starter. Then they changed gears, going with the tag-team duo of Chase Garbers and Brandon McIlwain to provide a mobility element. The melodrama went on for weeks, a mix of highlights and train-wreck moments. Now Garbers, a redshirt freshman, appears to be the one and only.

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Pac-12 bonuses: Larry Scott's move won't play well on campuses The turnover factor: Garbers’ production was modest last week at USC — just 93 passing yards in the win — but the Bears didn’t beat themselves. Cal is tied for second-to-last nationally with 23 turnovers. Sixteen of those came in their four defeats, leading to an obvious conclusion: If the Bears can merely hold onto the ball, their defense gives them a chance.

Muscle memory: Stanford has won the past eight Big Games, the longest streak by either team. Does the past matter? In this case, only so far as no one on the current Stanford team has ever lost to their rival. It’s not everything, but confidence counts.

Bottom line: The even-year Big Games are often the best. Why? At Berkeley, anything can happen. And that goes well beyond The Play in 1982. Most of the least predictable outcomes in the series have happened at Memorial Stadium. But exactly what would constitute a surprise result this time? The gap has closed and The Axe is up for grabs.