"He's the type who'd play with a plaster on his leg," said manager Alex McLeish. "We have to make sure we're satisfied with his fitness."
McLeish spent more than Birmingham had ever paid for a defender -- $8 million -- to take Johnson from Championship side Cardiff City in 2009, and he hasn't missed a league match since. Johnson and Scott Dann, who arrived from Coventry at the same time, soon formed a formidable central defensive partnership that shut out Manchester City and Chelsea and restricted Manchester United and Arsenal to a single goal (and a single point) at St Andrews last season.
According to Dann, the duo "just clicked," and McLeish describes the contrast in the team's resilience between when he took over three years ago and now as "night and day." McLeish doesn't want to disrupt things if he can help it, but he's also wary of risking a longer layoff; having made the most blocks and clearances, Johnson is "a vital component of the team." The player himself looks unflustered when we met at Birmingham's training ground. "I'm planning to make it," he said, smiling.
Such determination became a theme as we talked about his rise to the Premier League from League Two (England's fourth tier), where he was playing with Wycombe Wanderers until four years ago. "I always wanted to be playing in the highest league possible," he said, explaining why he ignored overtures from League One clubs to make the leap straight to the Championship when Cardiff came calling.
"You have moments where you think it's not going to happen, and you can only do what you can do. There are some great players in the Championship. Making it is about getting the chance, first and foremost, but I have a will to win, to achieve and not let anyone down. I don't like losing. It's about all those things together."
Johnson has benefited from working with McLeish, a defender in the same "aggressive" mold. "I'm always thankful for the opportunity," Johnson said. "When I came in, he just said, 'I want you to be big part of what we're trying to achieve here.' We probably view the game in the same way. ... He wants us to defend, not to complicate things."
Not that the top flight hasn't required some adjustments. "I'm not going to lie, you've got to keep your side in the game, so it's a big pressure," Johnson said. "If you make a mistake you get punished, so it takes more concentration than it did before. I've looked at my passing, too. In the lower leagues there aren't many people that come and want the ball, so you're trying to pick out a great pass. Now I'm playing with better players, every one comes to feet. I feel as though I've got a lot better."
Like McLeish, Johnson welcomes the arrival of quality players such as former Arsenal midfielder Alexander Hleb and one of the stars of Chile's World Cup team, Jean Beausejour. But he's not one for being star-struck -- he struggles to name a player he idolized growing up ("I just loved watching football"), and isn't overawed by any of the strikers he has come up against in the Premier League.
"I'm not being big-headed," he said. "I just relish every sort of opponent. I don't mind the fast little quick ones, I don't mind the strong ones. Every game in this league is a great game and I love all of them."
His only dread, he insists, is slipping up. "Mistakes happen 100 times in one game, it's just whether the crucial one is you. I try not to make any errors that are going to cost my teammates."
Having grown up supporting Chelsea ("They weren't great back then"), he's pleased, though, to be drawing comparisons with John Terry. "I like how he went about the game, coming through the youth team and ending up captain," Johnson said. Johnson -- whom McLeish refers to as "the big fella" -- recently captained Birmingham for the first time and it's a role that suits him. "I've always been outspoken. I'm a highly competitive guy," he explained.
Apart from the odd chick flick, his interests beyond soccer spread only as far as other sports -- darts and golf -- and he describes the buzz of the latter as "getting your handicap down as low as you possibly can." He's eyeing fellow defender Stephen Carr's club-best five or six as a target.
Johnson is about as laid back as they come -- yet his ambition is unmistakable. At 27, he's one of the in-form English defenders and there's a swell of public opinion pushing him into Fabio Capello's thoughts, but you sense that this was timed to come slightly sooner in Johnson's plans. At least, he said, another good season will give him two impressive Premier League campaigns by the time he's 28. Beyond that, Johnson has his sights set on making his mark further up the table.
"I'm not saying I deserve a move now, and I'm not saying, 'Come and get me,' " he said, aware of the perils of such conversations -- especially when whispers have suggested offers from bigger clubs might be in the cards. "But I'm not going to say I don't want to play for a top-six side; I'd be stupid if I did. Anybody should want to go and battle in Europe and challenge at the biggest sides."
For now, however, establishing Birmingham City as a credible Premier League outfit is front and center. Last year's ninth-place finish surprised everybody, and with continued investment -- close to $48 million has been spent on new players since the summer of 2009 -- hopes are high that a club with a history of bouncing up and down can now stabilize in the top flight.
"There have been a few stupid quotes chucked around that we're going to challenge for Europe, but the target is safety," Johnson said.
McLeish, too, has tried to temper expectations. "We know we're not going to be among the Manchester Uniteds; chasing Aston Villa is hard enough," he said, ahead of a weekend that Birmingham starts just a point behind its rival.
"I'm sure the owners are wanting things to happen quicker than they probably will with the money they've put in so far," Johnson said, "but football's not like that. We just need to stay in the league and build again next year. We've got realistic ambitions. If we finish 17th, we're still in the league."
Speak to either Johnson or Dann and you'll find a player completely enamored with having found his way to the Premier League, and determined to make the most of it. The season is long and unpredictable, but it's hard to imagine too many strike forces running rings around them fast enough to send them, and Birmingham, back down this year.