There are lots of reasons to be positive about England so far at this World Cup but having a settled side is not one of them. The main aim was to top our group, and we did that, but we have arrived in the last 32 after so much chopping and changing in several positions that we are no closer to knowing what our best team is.

It feels like Thomas Tuchel is still searching for some solutions, three games in. You don't have to have all the answers, even at this stage of a tournament - injuries and suspensions mean teams always have to adapt ideas and personnel as they progress - but Tuchel has quite a lot to sort out before we face DR Congo in Atlanta on Wednesday.

There is no doubt he is trying to find which combinations of full-backs and wingers work best for the team on both flanks - there have been nine different ones already across 270 minutes, involving eight different players. The reason Tuchel has tried so many is that he has not quite worked it out yet. Obviously the injuries to Reece James and Jarell Quansah at right-back have not helped and neither has Bukayo Saka not being 100% fit.

But, for whatever reason, we have not posed a consistent threat down the flanks and constantly changing the back four has not helped our defensive stability either. We've looked uncomfortable whenever teams have attacked us, which is a worry. At the same time, though, there have been several players who have produced. Elliot Anderson was absolutely superb against Panama, while Jude Bellingham was man of the match and rightly so, and Harry Kane got his goal, again. Along with Jordan Pickford and Declan Rice, they are the spine of the team and you know you can hang your hat on them when it matters.

Maybe we haven't seen as much from every part of Tuchel's team as we'd like, but we still know we can rely on our big-hitters to step up and produce something brilliant to change the course of the game. Ideally, we wouldn't be relying on someone to get us a goal out of nothing, like Jude Bellingham did when he turned in Saka's corner against Panama.

I'd prefer it if our system was providing us with a platform for creating lots of chances in open play, but there are going to be times like that in every game where things are not working for you. It is not as if we were looking dangerous before we scored, but we already knew how important set-pieces are and it's certainly not a bad thing to have big players you can rely on to provide a magic moment like that when the team needs it. It wasn't even a particularly good ball in, but Bellingham made it into one. Say what you like about the defending, but it was still impressive how he got on the end of it, showing his strength, balance and skill.

After he scored, there was only going to be one winner. DR Congo are likely to set up like Ghana and Panama, by defending in numbers and looking to hit us on the break. Again, the challenge will be to break them down - and it's a chance to show what we have learned.

Part of that might be as simple as the way we put the ball into the opposition area. As I said when I was covering the Panama game for Radio 5 Live, we had our wingers, Marcus Rashford and Saka, cutting inside to putting inswinging balls in - Rashford with his right foot from the left and vice versa with Saka from the left - which are easier for defenders to clear. We look more dangerous when they go on the outside then put crosses in, like Bellingham did for Kane's goal. That way, the forward can make his run once he knows it is coming, and attack the ball.

Between them, Rashford (number 11) and Saka (number seven) attempted nine crosses in open play against Panama. None of them were successful - as in they found a team-mate. We have not seen the best of this England team yet going forward but my biggest concern so far is how many times we have been opened up at the back. It's happened in all three games - we were poor defensively in the first half against Croatia and conceded twice, but we got away with it against Ghana and Panama despite being shaky and giving them chances.

Big improvements are needed because the further we get in this tournament, the better opposition we will face. Those better players will punish us if we keep doing the same things, and it will also be harder to recover from those mistakes. At past tournaments, even if you could argue our defence was not the strongest, at least it was always pretty settled. But it looks like we will have a different back four again against DR Congo, with either Spence coming in again at right-back or Erzi Konsa moving across from centre-back and maybe John Stones partnering Marc Guehi - if he's fit.

Some of the changes Tuchel has made so far have been his choice, but others have been forced on him. As I said earlier, injuries affect everyone but he has taken a massive gamble with some of the players he has selected because they have a history of getting injured. Whoever he chooses in his back four against DR Congo, hopefully it works and takes us through the next couple of rounds, at least.

I am confident I will be asking how England get on against Mexico or Ecuador next, but if we are going to go far at this World Cup then we will need to stop shifting players around and find some stability at the back.

Alan Shearer was speaking to BBC Sport's Chris Bevan

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